The episode unfolds with Harry Bell (Tony Curran), Allen Feraday (Nicholas Gleaves), and Ed McCusker (Connor Swindells) stepping into the RARDE facility in Kent, England, their identities verified by a vigilant security guard. Moments later, Feraday captivates Harry and Ed with magnified views of the shard fragments, freshly cleansed by ultrasonic waves, retrieved from the bombed luggage pallet. He highlights the AG145 production marking on the pieces, meticulously explaining how they pinpointed it as the bomb's remnant.
Displaying a magnified image of the shard's reverse side, Feraday draws attention to the SRBP-printed circuit board, a common component in radios. By deciphering the manufacturer ID "L106" and the distinctive diamond-shaped diagnostics, he identifies the radio as a Toshiba model. His hypothesis: a German bomb-maker has adopted Toshiba radios for his sinister purposes.
Meanwhile, from the confines of a vehicle, Hans-Jurgen Sonntag (Peter Svatik) snapshots Marwan Khreesat (Salah Hanovun), a suspected German bomb-maker, through the window of his apartment. Ursula (Blessing Osadolor) swiftly informs the dispatch of Khreesat's movements. Sonntag and Ursula trail him to a public phone booth, where a car parks nearby. The Operation Autumn Leaves unit swiftly arrives on the scene, apprehending Khreesat and the driver. Sonntag pops open the trunk to unveil an assortment of bomb-making apparatus. A bomb technician meticulously scours through the components and unearths a Toshiba BomBeat radio.
Flashback to February 2, 1989, a crucial 43 days preceding the bombing. John Orr (Peter Mullan) dials DCS Manfred Klink (Rainer Sellien), seeking insights into Operation Autumn Leaves. Klink had previously warned Interpol two months before the Pan Am 103 disaster. He clarifies that Autumn Leaves was initiated in response to domestic terrorism threats, casting doubts on its connection to Pan Am 103. He reveals that 17 individuals, Khreesat among them, were apprehended. Dick Marquise (Patrick J. Adams) mentions the Front of the Liberation of Palestine General Command (PFLP-GC), which employed Khreesat, having been under his radar for some time. Suspecting Iranian funding behind PFLP-GC, Marquise posits a potential link.
Klink discloses that the confiscated Toshiba BomBeat radio was programmed to detonate at cruising altitude, authorizing its reexamination. He notifies them of Khreesat's release due to insufficient evidence, mere weeks before Pan Am 103. Khreesat might have retreated to Jordan. Marquise hints at German officials' fears of inadvertently freeing the Pan-Am bomber, before concluding the call.
Turman strides up to Marquise and introduces herself as a staffer for Senator Heinz. He acknowledges her previous phone calls, which he hadn't replied to. She then recounts how she became entangled in the case following Pat Noonan's desperate pleas to Heinz's office, which, along with Pan Am and the State Department, had fallen on deaf ears. (It's worth noting that she once headed the FBI's Victim Services Division.) Marquise lambasts Pan Am for abandoning the victims' families. She insists that the FBI has also let them down, griping about the absence of a victim liaison within the United States. Marquise emphasizes that the FBI's priority is to forestall a recurrence of such attacks and safeguard the families' welfare. Turman asks if Marquise would honor her calls in the future, and he agrees to provide her with a direct contact number.
Orr reveals his plan to Ed, outlining his vision for a satellite Holmes office in Washington D.C., tasking Ed with an indeterminate stay there. Afterwards, Ed confides in June McCusker (Lauren Lyle) about Orr's proposal. She urges him to seize the opportunity. He cautions that it could entail a commitment spanning several months or even longer, as the FBI requires access to their database. Meanwhile, Sandy arrives at the academy and engages Ed in a conversation about relocating to America. Sandy envisages Ed thriving in the new environment. Ed scours the Holmes system for any mention of Toshiba or radios, but comes up empty-handed. Sandy suggests that Feraday's shard might be the sole remaining clue, possibly planted in a box to give the radio an air of novelty. Ed discovers a solitary entry for an instruction manual, believing it must be housed at Dexstar. He ventures there with Harry to search for the elusive document. They uncover the remains of a BomBeat instruction manual, which Harry identifies as the same model as the bomb discovered in Germany. Orr informs the team that evidence suggests a two-speaker BomBeat was responsible for bringing down the plane. The suspected bomb-maker is Marwan Khreesat, known for using such radios. In 1970, Khreesat's bomb killed everyone on a flight from Zurich to Tel Aviv. Orr speculates that Khreesat was likely the bomb-maker behind that attack too. Once a prominent bomb-maker for the Popular Front, the FBI believes he left the cell a decade ago but was later recruited for a high-profile mission.
Harry asserts that this information also aids in identifying the bomber's suitcase type. To date, authorities have recovered 27 pieces of sturdy Samsonite luggage, each with a distinctive hard shell. Inside one such Samsonite case, they discovered both the manual and the radio bomb. However, matching this suitcase to a specific passenger remains elusive. This particular suitcase belongs to the exclusive Silhouette 4000 collection, of which only 487 units were produced and sold in the Middle East and North Africa. Additionally, the suitcase likely contained a baby's onesie and a pair of folded trousers. Orr emphasizes the urgency of locating Khreesat, while Ed diligently works on integrating the Holmes system with the FBI.
At the US Consulate in Zurich, Switzerland, Bollier is grilled about the letter he left at the Vienna embassy. He insists he's guiding investigators in the right direction, but the female interrogator remains skeptical. Dick is informed that Bollier is perceived as eccentric, possibly unstable. Dick inquires about Khreesat with Gabe, who suggests looking towards Iran. Dick mentions the incident where a US naval vessel mistakenly shot down Iran Air 655, to which Gabe responds that they were unaware it was a passenger jet. Their conversation escalates, touching on the topic of Khreesat and the ineptitude of their public relations compared to their adversaries. Gabe initially hesitates to grant Dick access to Khreesat but eventually concedes, albeit reluctantly.
Elsewhere, Ed engages in a heartfelt conversation with Steven Flannigan, alias Archie McCormick, about his impending trip to America. As a token of his absence on Flannigan's 15th birthday, Ed presents him with a gift and bids him happy birthday. Volunteers tirelessly continue packing the victims' belongings, with Moira advocating for the inclusion of every item, believing that the families should decide what holds significance. Ed arrives to collect a box destined for America, to which Moira Shearer adds a memento from Lockerbie. The team has faced some volunteer attrition. Ed carries the box out, reassuring June of his prompt return and bidding farewell to the female volunteers before proceeding to the airport.
Tom Thurman confides in Dick Marquise his intent to detonate a plane, prompting Dick to inquire about the purpose of such an action. Tom proposes procuring Toshiba BomBeat radios and packing them with Semtex to perhaps verify that the bomb originated in Frankfurt rather than Heathrow. Tom wonders if the CIA remains tight-lipped about Khreesat, to which Dick confirms he has officially requested assistance. Both acknowledge that spies often know more than they disclose. Dick assents to Tom's bomb test, stipulating that it must be funded from his budget. Meanwhile, Ed arrives and is whisked away to the Federal Bureau of Investigation, where he meets Phil Reid.
Phil informs him that the Holmes room will be detached from his office space, emphasizing their eagerness for a comprehensive presentation elucidating its operations. Bob Monetti, alias Robert Jack, and Joe Horgan, known as Joe Layton, greet Kathryn Turman, portrayed by Merritt Wever warmly. Kathryn is aware that they are actively lobbying the White House to establish a President’s Commission, aimed at scrutinizing aviation security. Their endeavor stems from their representation of the victims of Pan Am Flight 103.
Yossi Langotsky's security firm had, two years prior, issued a report to Pan Am, warning of the airline's vulnerability to mid-air explosions caused by charges in the cargo. Kathryn underscores that it is the poignant human stories that resonate with senators and congressmen, transcending partisan divides. She reveals that a journalist deceitfully obtained their phone number from Syracuse University, which is how Bob and Joe discovered their son perished on the flight. Joe brings up Ed McCusker, suggesting Kathryn should meet him. Bob mentions the Scottish families' plight, forced to retrieve their loved ones' bodies wrapped in grim, soiled cardboard.
Bob begins to recite excerpts from Rick's journal while Ed enlightens the team about the Holmes database. He explains that in Scotland, a detective personally oversees the database to ensure precision, necessitating an explanation of this unique approach. Ed emphasizes that Holmes operates as a collaborative team system and expresses hope that they will crack the case together.
Later, Ed meets Kathryn, and they embark on a stroll, discussing Joe Horgan and Nazir Jaafar, who is filing the first civil claim against Pan Am. Their conversation delves into the heart-wrenching stories of the victims. Ed introduces Kathryn to the volunteers involved in the case. Meanwhile, Sandy pays a visit to Moira, who invites him to join Mia, played by Monica Lopera. Mia expresses her desire to witness the site where her mother's body fell, prompting Sandy to show them the location. He also shares his vivid recollections of the tragic first night.
Harry is shown a picture of Yorkie trousers, sparking an investigation into the Yorkie brand. Elsewhere, Ed transports a box to a house, while Harry and Allen arrive at the airport, requesting Ed's briefing. Harry expresses frustration over the FBI's continued refusal to grant them access to Khreesat.
Harry insists that they are the ones pitted against the entire world, stirring up a tempest of controversy. Allen scoffs, asserting that DCI Bell is incapable of unraveling the enigmatic Yorkie trousers case, his demeanor far from amused. The crucial bomb tests commence at the Indian Head Naval Research Center, nestled in Maryland, with Tom serving as their meticulous guide through the intricate process. Their objective: to ascertain whether a bomb concealed within a Toshiba BomBeat could have wrought the observed devastation.
Dick's curiosity peaks, wondering aloud if Khreesat was indeed the perpetrator behind the explosion. Allen, ever the rational scientist, dismisses such inquiries, emphasizing that science's purview does not extend to the guilt or innocence of suspects. He contends that if they can successfully recreate the explosion's true impact elsewhere, Khreesat's involvement would be conclusively negated. They delve into various hypothetical scenarios surrounding the blast, each attempting to piece together the puzzle.
Allen theorizes that the explosion's impact was mitigated by adjacent luggage, creating a cushioning effect. Tom concurs, acknowledging the complexity of the plot yet emphasizing the element of sheer chance that factored into its success. Allen then proposes a scenario involving the cases loaded at the bottom of the pallet destined for London, but this hypothesis too falls flat. Tom becomes increasingly convinced that the culprit was a Frankfurt-bound suitcase, leading them to experiment by relocating the hypothetical bomb to the front left corner, near the overhead compartment.
Upon testing this arrangement, Tom declares with certainty that they've hit the mark—proving beyond doubt that the bomb originated from Frankfurt. The tension eases, and the team celebrates with a well-deserved night out, enjoying drinks and dining together. Amidst the revelry, Ed engages Dick in a conversation about the intricacies of being an agent and the broader threats they face. Dick emphasizes the omnipresence of international terrorism, revealing their reliance on the CIA to combat this pervasive menace.
When Ed inquiries about Khreesat, Dick admits that no progress has been made in that front. Just then, Gabe Lepley (played by Terence Maynard) bumps into Dick, excitedly informing him that he's secured access to the Jordanian bomb-maker. Dick stands poised to fly to Amman at a moment's notice, with strict instructions to keep the Scots in the dark. Gabe stresses the importance of maintaining their alliance with the Jordanian secret service, a pivotal player in the region.
Elsewhere, Manfred Klink contacts John Orr with grim news. During a re-examination of Khreesat's devices by one of their agents, Hans-Jurgen Sonntag, a device unexpectedly detonated, fatally injuring Sonntag and seriously wounding his colleague. Klink acknowledges the pressure to stay ahead of the narrative, ordering another exhaustive search for the luggage manifest. The stakes have never been higher, as each revelation draws them closer to the heart of a labyrinthine conspiracy.
In Amman, Jordan, Dick and Ed Marshman arrive and are promptly escorted to Marwan Khreesat. Dick confronts him, stating their awareness of the radio bomb he constructed, which was confiscated by the BKA on October 26th. A device eerily similar to his handiwork had tragically brought Pan Am Flight 103 to its downfall. Dick inquisitively presses for information, and Marwan concedes, admitting that he crafted Toshiba BomBeat bombs for an undisclosed organization. He reveals the acquisition of five radios, which unfortunately found their way into Germany. He insists, however, that only the single-speaker models were utilized. Ahmed Jibril had sanctioned the deployment of these devices, and Marwan suspects a plot targeting an Israeli airline was in the works.
Upon their arrest by the BKA, one such device was discovered in their vehicle, though fortunately, it was rendered harmless. Dick informs Marwan that one of his creations had recently claimed the life of a BKA agent, clarifying that he himself hadn't armed the recent bombs, but Jibril's men might have. Marwan claims he severed ties with the group in 1973, returning to Amman to establish an electronics shop. Years later, Jordanian police agents approached him, proposing a return to the Popular Front in Germany as an informant. Dick counters that they've essentially employed a known killer, to which Marwan responds that he faced an ultimatum: become a mole or witness his family's suffering. He opted to relocate to Germany, potentially feeding intelligence to the CIA.
Marwan steadfastly maintains his innocence, insisting that his radios couldn't have been involved as he solely produces barometric detonators. He's convinced that his creations have been surpassed and duplicated by various freedom fighters globally. With an air of superiority, Marwan asserts that they're outmaneuvering both the FBI and CIA.
Outside, Dick vents his frustration to Marshman, branding Marwan a murderer, albeit not their target, and suggests that the CIA was privy to this information. He laments feeling handicapped in their pursuit. Meanwhile, Orr uncovers that Khreesat has been a deceptive decoy from the outset. Dick ponders over a shoe's photograph post his conversation with John Orr. As Orr receives the Frankfurt list, Ed dials June, updating her on his endeavors and suggesting she and the children join him temporarily. June, rooted in Scotland, declines, expressing her love for their home. She seeks his understanding for not altering her plans.
Harry is briefed on the luggage manifest, revealing that Flight 103A carried seven pieces of interlined luggage, with hold luggage transferred between airlines. One suitcase notably lacked a corresponding passenger, tracing its journey from Malta to Frankfurt via flight KM180. Intriguingly, a Yorkie Trading Company is located in Malta. With this revelation, Harry is summoned to board another flight.
