Edward Brooks (Leo Woodall) and Taylah arrive at the bustling airport, swiftly hopping into a waiting taxi. Kasim (Mudar Abbara), hot on their trail, leaps into another cab in pursuit. As they settle in, Taylah dials Jane, relaying their safe arrival. Jane confirms her suspicion about the NSA's Syracuse operating system being compromised and instructs Taylah to report back.
Scanning through Edward's portfolio, Andrew Carter (Harry Lloyd) can't help but be amazed by his intellect. He confesses to having Kasim tail Edward and Taylah, prompting Jane to issue a stern warning—if anything untoward happens to Taylah, he will be held accountable.
In Baghdad, Edward is engrossed in reading messages from Adam Mellor (Fra Free) when Taylah abruptly interrupts him. Meanwhile, at the excavation site, Professor Andrea Lavin (Sidse Babett Knudsen) meticulously translates tablet 5, her eyes scanning through a treasure trove of artifacts that Dr. Akram Nizar (Ali Suliman) informs her were discovered on the chamber floor. Holding up a coin, she reveals its 17th-century French origin, suggesting that others had been there before them. She instructs Akram to delve into records of any excavations conducted in the 1600s.
A call from Edward interrupts her thoughts, requesting a meeting. After hanging up, Andrea informs Akram that she'll be meeting with a former PhD pupil of Professor Robert Mallinder (David Morrissey). Akram mentions the tragic gas explosion that left five dead and many injured.
Over at Abbas Café, Taylah spills the beans to Andrea, asserting that Robert was murdered. Andrea demands concrete evidence, her skepticism evident. Edward reveals Taylah's NSA agent status, while Taylah alleges that the NSA has had Andrea and Robert under surveillance for years, hinting that Robert's last email was AI-generated, potentially linked to his groundbreaking work on prime numbers—a field Edward is also deeply involved in. Andrea, who never believed Robert took his own life, still refuses to aid them.
From a nearby table, Kasim keeps a close eye on their conversation. Back at the hotel, Andrea listens intently to Robert's final voicemail, lost in thought. Elsewhere, Edward quizzes Taylah about why she sought him out. She claims a motorcycle accident led to the tragic death of her lover, prompting her to seek refuge with her godmother, Jane. Edward believes that discoveries and ideas are neutral; it's how they are used that determines their essence. Taylah counters, arguing that this is merely an evasion of responsibility. Edward stands firm, asserting that the truth cannot be silenced and refuses to abandon his ideas.At the NSA headquarters, Andrew imparted to Jane the authorization to terminate Edward. She revealed that Edward was scheduled to visit the archaeological dig site. Stepping outside, Jane dialed Taylah and instructed her not to accompany Edward to the dig. Taylah hesitated, questioning the morality of the directive. Jane persisted, securing her promise as Taylah terminated the call.
Moments later, Andrea assured Edward that Robert's final voicemail contained no anomalies, with Kasim trailing behind them. Jane inquired about Taylah's reliability, to which Kasim attested to her honesty thus far. Reporting back to Jane and Andrew, Kasim noted Edward in the company of an elderly woman, while Taylah was visible at the bustling market. Edward speculated that Andrea's tablecloth might be linked to Robert's demise. Believing Taylah was absent, Jane commanded Kasim to eliminate Edward.
Witnessing Kasim gripping a knife, Taylah hastily navigated through the crowded market to catch up with Edward. He suspected Robert had withheld crucial information, believing the answer lay within the chamber. Meanwhile, Bogdan Viahovic (played by Sergej Onopko) confronted Kasim, igniting a scuffle. Kasim sliced Bogdan's arm, prompting Bogdan to ensnare Kasim's neck with a cloth and choke him to death. Bogdan fled before Taylah arrived to check for a pulse. She inserted Kasim's earpiece, hearing Jane inquire about the mission's status. As she reached Edward, he inquired about her distress, which she promised to explain later. Akram requested her to wait while he showed Edward the dig site, emphasizing its sentimental value as the birthplace of revolutionary ideas.
While Andrea deciphered ancient inscriptions, Edward unlocked their secrets. Taylah noticed Bogdan bandaging his wounded arm and snapped a photo. Edward grew anxious upon learning some inscriptions had eroded. Andrea persuaded him to take a break. Taylah conducted an image search to identify Bogdan, unaware of Akram's watchful eye.
At the NSA headquarters, Andrew displayed crime scene photos of Kasim's lifeless body to Jane. He revealed another entity was trailing Edward, suggesting they remain inconspicuous until the "holy grail" was found. Andrew emphasized the necessity of Taylah's cooperation and queried her trustworthiness. Jane assured him of her reliability. He stressed that if they couldn't prevent the weapon's creation, they must control it.
In the bustling city of Baghdad, Hassan Kasem, portrayed by Sia Alipour, confides in Andrea, revealing himself as a compatriot of Dr. Charan Nathoo, played by Maanuv Thiara. He hands her a meticulously prepared report detailing the explosive demise of Bayt al-Hikma, cautioning her to maintain a healthy skepticism towards everyone at the excavation site before hastily departing. Andrea, intrigued, presents the report to Taylah, who scans through the findings, revealing that the destruction of Bayt al-Hikma was a deliberate act, orchestrated by an explosive device. Andrea ponders aloud if Charan and Robert were perhaps victims of the same adversaries, prompting Taylah to vow to uncover the truth.
As Taylah delves into Akrim's past, her eyes catch him in conversation with Bogdan. Meanwhile, Andrea photographs the dig site, using a magnifying glass to uncover suspicious paper fibers. She educates Taylah on the art of Estampage, an ancient method of stamping used in epigraphy, emphasizing that ancient inscriptions often reside in museums. Akrim's curiosity peaks as he inquiries about their progress, but Andrea swiftly interjects Edward before he can divulge too much. As they depart, Andrea whispers a warning to keep their discoveries under wraps. Akrim, examining Andrea's photos, recognizes the intricate details of Estampage.
Elsewhere, Taylah immerses herself in Ricky Olson's emails, retrieved from the NSA database. In one particular email to Jane, he urgently requests a meeting to discuss Mallinder. Her phone buzzes with a message from Jane, urging her to return to Paris at once. In parallel, Andrea delves into museum archives, while Edward tackles the task of decoding the enigmatic ancient script.
The following morning, Andrea presents Edward with a revealing archive photo, depicting the upper portion of the Mersenne Collection. She insists that he travel to Orleans, France, to witness the entire panel. Taylah interrupts their conversation with a startling revelation: Bogdan had intervened to thwart an assassination attempt on Edward at the market. Andrea recognizes the man as one she had seen at the dig site. Despite Jane's persistent calls, which Taylah ignores, she shares that Edward's life hangs in the balance, with some desiring his demise and others wanting him alive. Stressed, Edward inquiries if Kaplar is involved, and Taylah proposes a visit to Orleans to uncover the missing section, vital for constructing the prime finder. She cautions Andrea about the dangers lurking in Orleans.
Undeterred, Andrea insists on staying until the chamber is fully documented, handing Taylah a USB stick laden with her translations. Meanwhile, Andrew and Jane scrutinize CCTV footage showing Kasim and Bogdan in a fierce altercation, culminating in Bogdan's fatal strike. Jane, desperate, texts Taylah, pleading for her return to Paris. Edward persuades Taylah to take Jane's call, where Jane informs her that two tickets to Paris await them at the airport. Taylah, responding with a mixed sense of sympathy and indifference, comments on Kasim's untimely demise. Upon reviewing the CCTV footage, Jane notices Taylah rushing to Kasim's lifeless body, placing his earpiece in her ear, revealing a deeper connection to the unfolding mystery.
