Episode 7 kicks off with Father Brown (portrayed by Mark Williams) stepping into the dreary confines of a prison cell to visit Samuel Harrow (played by Paul McEwan), on behalf of the distressed Lady Felicia (Nancy Carroll). Harrow, unburdening his soul, freely concedes to Felicia's suspicions, asserting his innocence in the grim murder of her goddaughter, Sophie Blackthorn (Sophie Blackthorn). Armed with this revelation, Father Brown conveys the message to Lady Felicia, prompting them to embark on an investigation of their own accord.
Gathering at an intimate setting, Lady Felicia convenes with Father Brown, Brenda Palmer (Ruby-May Martinwood), and Isobel Devine (Claudie Blakley) to dissect the case and delve into her unwavering conviction of Harrow's innocence. At the heart of her belief lies a letter and a haunting encounter with a youth named Daniel Price (Tom Blupett), who harbors suspicions pointing towards Sophie's husband, Ralph Blackthorn (David Burnett). Despite Father Brown's meticulous perusal of the letter, its enigmatic contents remain elusive to the gathered group.
At Lady Felicia's urging, Father Brown, Devine, and Brenda venture into the prestigious halls of the Blackthorn Institute, a bastion of crime-solving methodologies and technologies. This very institution, with its elite staff, including Professor Prichard (Silas Carson), played a pivotal role in Sophie's probe. An awkward encounter ensues when Devine finds herself in an embarrassing cutting predicament with Professor Prichard. Meanwhile, Father Brown and Devine serendipitously cross paths with Daniel Price, who is likewise revisiting Sophie's case with renewed vigor. Daniel shares his latest findings, only to be abruptly interrupted by Brenda, who urgently needs Devine's car keys to tune into a horse race.
Elsewhere, Felicia's path crosses with an old acquaintance, Audrey Hatby (Belinda Owusu), who巧合地 serves as Prichard's assistant. The gathering's attention shifts to Ralph as he raises a toast to Sophie's memory, expressing gratitude to Professor Prichard for his unwavering support of the institute. However, the solemn moment is shattered by the sudden arrival of a Pattinson Butcher delivery man, bearing a gruesome package—a bloody pig's heart, as identified by Prichard.Ella Blackthorn (Kate Bracken), in an attempt to dismiss the erroneous delivery as a mere mistake, found herself ill-prepared when Brenda returned, only to discover that most of the guests had already departed. Prichard, eager to impress, offered Father Brown and his companions an exclusive, behind-the-scenes glimpse into the inner workings of the institute and his laboratory. However, this intimate tour was abruptly halted by Daniel's intervention, which did not sit well with Prichard, who responded harshly.
Moments after Prichard's curt rejoinder, Daniel was seen ingesting some form of medication, only to suffer a seizure shortly thereafter. His final, garbled words were, "Notebook." As Inspector Sullivan (Tom Chambers) grilled the remaining guests collectively, Prichard bristled at Audrey's suggestion that Daniel had been poisoned. Ralph, meanwhile, exhibited a hint of irritation when Sullivan made a callous remark about death seemingly trailing him.
With the storm brewing outside, Prichard persuaded Sullivan to conduct an autopsy at the institute, which subsequently validated Audrey's suspicions of poisoning. Later that evening, while perusing Prichard's notes on the Harrow case, Father Brown and Felicia stumbled upon copies of the taunting letter that Harrow had sent to the widowers. Sullivan arrived just as they realized that the letter intended for Ralph was missing. Upon confirming that the poison originated from the institute, Sullivan seized control of the files.
With Sullivan and the case notes now absent, Father Brown and the group were left to ponder the fate of the notebook. Audrey speculated that it had been stolen and subsequently incinerated, a suspicion later confirmed during a visit to the building's incinerator. Ralph, steadfast in his assertion of innocence, admitted to destroying the letter when questioned by Sullivan, to no avail; Sullivan proceeded to arrest him nonetheless.
Upon learning of Ralph's arrest, Father Brown discreetly approached Felicia, inquiring whether she still believed in Ralph's innocence. She affirmed her conviction, asserting that Sophie would support her stance. In return for her cooperation and insights into Ralph's character, Father Brown vowed to exhaust every avenue to prove Ralph's innocence.Father Brown bestows upon Ralph an identical pledge and inquiries into the essence of the letter's contents. Ralph confesses to having obliterated it, as it cast a shadow of guilt upon him. He further acknowledges having endured a harsh and destitute upbringing, marked by brutality. As Ralph casually remarks that everyone, even Prichard, could perceive his affection for Sophie, Father Brown's suspicions shift towards the Professor.
Prichard acknowledges his fondness for Sophie but asserts that witnessing her bliss with Ralph sufficed for him. During his search of the darkroom for duplicates of photos from Daniel's camera, Father Brown deduces that this very spot might have been the point of entry for someone to tamper with Daniel's medication. His suspicions then pivot towards Audrey, as Devine reveals that it was she who illuminated the poison.
Upon confronting Audrey with this newfound information, Felicia discovers that Audrey's mother was once in the employ of Sophie's family. A shattered vase would not merely result in her unemployment but would also force Audrey to abandon her education to shoulder the financial burden. Father Brown is startled to uncover that Daniel's life has been a series of in-and-out stays in mental institutions, just as Ella arrives, incensed that Sullivan left Ralph unattended and handcuffed.
The ensuing storm knocks out the power, prompting them to scavenge for candles and flashlights. After reuniting with the rest, Felicia sets out to find Devine, who had become separated from Brenda. Brenda finds herself intrigued by the red bulb in Audrey's light, which Audrey explains was tailored specifically for the darkroom. Led by Audrey's mention of someone leaving a mess, the group returns to the darkroom. With Audrey's assistance, they uncover duplicates of vehicle tire prints.As Felicia searches diligently for Devine, she overheads Ella assuring Ralph of her unwavering protection. Ralph, in response, insists that she has gone above and beyond, particularly when she deceived the police on his behalf. Meanwhile, Brenda, Father Brown, and Audrey are immersed in scrutinizing photographs, with Prichard lending his expertise. Their analysis is interrupted by the arrival of Sergeant Goodfellow, played by John Burton. Upon hearing about Daniel Price's poisoning, Goodfellow reveals that he had met with Daniel two days prior, discussing stolen vehicles. He mentions a Pattinson delivery van that was erroneously flagged as stolen. Brenda swiftly connects this name to the van she had glimpsed earlier while tuned into the horserace.
Sullivan tracks down Devine but finds himself unable to gain entry due to a locked door. As he struggles with the lock, he is suddenly attacked from behind. Elsewhere, Father Brown, Brenda, and Felicia step out into the hallway to delve deeper into their discussions about the evidence. Their conversation is abruptly halted by Devine's desperate cries for help echoing through the corridors. Upon discovering Sullivan and Brenda, Sullivan realizes with a shock that his handcuff keys were pilfered during the assault. They swiftly confront Ella in the act of freeing Ralph. The revelation about the stolen delivery van leads to an unexpected discovery: Ella and Ralph are not related, despite Ralph's lifelong perception of her as a sibling and nothing more. It transpires that Sophie had witnessed Ella's amorous advances towards Ralph, which ultimately led to her untimely demise.
The episode concludes on a poignant note, with the unveiling of the institute's dedication to Daniel and the heartwarming news that Ralph is sponsoring Audrey's continued education.
