The episode kicks off with Father Brown (portrayed by Mark Williams) and Mrs. Devine (played by Claudie Blakley) arriving at Thorp’s Almshouses, ready to impart spiritual solace. Upon entering Adelaide Jenks’s (Ellen Thomas's character) humble abode, she confesses to battling insomnia but insists she hadn't sought their guidance. Mrs. Devine’s inquiry if another soul had summoned them prompts Father Brown to deduce that Jenks is harboring a gentleman in her single women’s quarters, contrary to the rules.
Jenks justifies her hospitality towards Harold, explaining his kindness following her husband’s demise. Harold chips in, mentioning their secrecy was due to Cormac Thorp’s (Daniel Tuite's portrayal) influence. Meanwhile, Brenda Palmer (Ruby-May Martinwood) teaches Eunice Lytton (Anita Dobson's role) the art of limbo when the dinner bell chimes, signaling the mealtime. Over dinner, the residents gripe about the dilapidated state of their almshouses. Thorp announces his intention to convene a meeting with the trustees the next day to lobby for funds to modernize their dwellings. Jenks attempts to covertly slip a bread morsel out of the cafeteria, only to be reminded by Thorp that inspections could occur at any hour. Father Brown’s attempt to steer the conversation elsewhere by requesting a tour falls short. Despite this, Thorp remains unsuccessful in uncovering any sign of Harold.
When Thorp eventually grants Father Brown a tour, it's abruptly halted by Eunice, who’s in the midst of burning her uniform. Thorp confiscates her matches and escorts her to his office. That evening, following Devine’s car troubles, Father Brown, Brenda, and Devine find themselves invited to stay the night at the almshouses. The subsequent morning, Devine embarks on a search for Harold and stumbles upon Thorp’s lifeless body.
Sergeant Goodfellow (John Burton) and Chief Inspector Sullivan (Tom Chambers) arrive on the scene, uncovering that Thorp plummeted from the roof while attempting to repair leaks. The moss clinging beneath his fingernails leans towards a conclusion other than suicide. Privately, Jenks reveals to Father Brown and Devine that Harold ventured out last night and hasn’t returned. Their conversation is abruptly halted as Father Brown is summoned to lead the 9 o’clock prayers, which are promptly interrupted by an eerily cheerful Eunice.As Goodfellow scours the rooftop, Sullivan uncovers Harold crouching in the concealing foliage, nabbing him just moments after the 9 o'clock prayer bells ceased their chanting. Harold's fate seals with the discovery of the flask, confiscated earlier from Jenks' quarters by Thorp, now in his possession. Amidst the escort of officers, Father Brown turns back towards the precinct, only to be intercepted by the trustees' arrival.
Incarcerated, Harold pleads intoxication as his alibi for the preceding night's events, confessionally admitting to Thorp's demise. Meanwhile, at the almshouse, Nora Thorp (Diana Hardcastle) informs the gathering that the trustees have postponed Thorp's meeting till the morrow, albeit with an uninvited guest—a sanitation inspector. Brenda and Devine, sensing the urgency, galvanize the womenfolk into a spree of housecleaning, aiming for impeccability before the impending visit.
Father Brown imparts to Jenks that Harold is now collaborating with the authorities, revealing his dying wish to know what she had discovered. Jenks unfolds her tale—a grim morning discovery of a deceased woman by the almshouses' gates, followed by Eunice's nocturnal entry into the church, shortly after Thorp. Eunice protests her innocence, asserting she was but a supplicant seeking solace, and casually mentions a hush-hush extortion plot involving Thorp. Father Brown's suspicions deepen, linking the timing of the inspection to Thorp's tragic end. His plea to peruse the trustee files for clues is met with a task assignment—to scrub Thorp's office clean. While immersed in this menial chore, Nora slips in, making off with the money.
Father Brown inquires of Nora whether her sense of entitlement to the money stems from her being a Thorp. She evades the inquiry, prompting him to pose another: could it be that she wishes to manage the almshouses? Nora responds with uncertainty, doubting her own competence for such a role.
Later that day, as Father Brown and Devine delve into the missing trustee papers, his gaze falls upon the syphilis scars adorning Gladys Carpenter's (played by Linda Thorson) hands. In a confidential moment, Gladys confesses her past as a streetwalker, acknowledging that Thorp had discovered her secret and attempted to blackmail her, though she vehemently denies any involvement in his murder. Their conversation is abruptly halted by Sullivan's arrival, bearing a special delivery of cleaning supplies for Devine. The women soon gather, the topic of murder piquing their interest, until Sullivan drops a bombshell: Harold has confessed.
Overhearing this, Jenks is overwhelmed with emotion, believing Harold is taking the blame for her. Her guard crumbles, confessing to Devine that she didn't merely discover the woman dead; she was her killer. In private, Jenks unburdens her soul to Devine and Father Brown, recounting how she failed to assist a homeless woman after Thorp denied her refuge at the almshouse. Upon inquiring about the registry list, Father Brown uncovers that Hannah Boyd was not the only soul Thorp had turned away. He later consults with Brenda and Devine, leading to a plan where Brenda will search the ladies' quarters during morning prayers.
Eunice catches Brenda in the act and tasks her with unclogging Gladys's toilet as punishment. While engaged in this unpleasant chore, Brenda stumbles upon what appears to be a shredded contract. She presents it to Father Brown, and together they devise a strategy to piece it back together. Father Brown then visits Harold in jail, seeking his assistance, but Harold sticks to his earlier claim of being too intoxicated to recall the events of the night Thorp perished. Their conversation is momentarily interrupted by Eunice's fall while attempting to clean the gutters at the almshouses, adding another layer of drama to an already tumultuous situation.
By the time Father Brown steps onto the ground, Nora and Gladys have already confined Eunice to her room. Through his perseverance, he eventually persuades them to allow Eunice to undergo a medical examination. Once she has been checked, he reveals to her that he is aware of her involvement in Thorp's demise and proceeds to unravel the manner in which he discovered the truth.
While awaiting his turn to speak with Thorp in his office, Eunice had chanced upon the contract for the sale of the almshouses. It transpires that Thorp had been undermining the properties in order to coerce the trustees into selling them to a company intent on converting them into retirement homes. Eunice, unable to keep this to herself, imparted the news to Nora and Gladys, prompting the trio to confront Thorp on the roof. However, it was Gladys who, in a moment of impetuosity, shoved him over the edge. She subsequently confesses her act to Chief Inspector Sullivan upon his arrival.
Scarcely has Gladys' confession left her lips when the sanitation inspector appears on the scene and declares the property fit for occupancy, albeit with a few repairs needed. Meanwhile, within the confines of Father Brown’s church, Harold and Jenks are joyfully reunited. As the episode draws to a close, Father Brown and the ladies of the almshouses give Hannah a respectful and heartfelt farewell.
