Marian has suspected that Sir Percival and Count Fosco are scheming against Laura, and now she has proof. Through a half-open door, she overhears the Count warning Sir Percival of Marian’s suspicions – but then he closes it. Desperate to hear more, Marian climbs onto the roof and perches on a balcony above the room’s open window. Sir Percival tells the Count that he must find Anne Catherick; he’ll lose everything if he doesn’t, because she knows his secret. And he also needs Laura’s inheritance, because he’s so deeply in debt. He would get it if Laura were to die. And the Count would receive a windfall, too, since his wife’s inheritance is tied up in Laura’s estate as well.
Deafening rain begins to thunder down. Laura and Anne bear a striking resemblance to each other, the Count points out. Why not use that to their advantage? The rain is too loud for Marian to hear anything more.
The next day, Marian takes ill – perhaps from the exposure. She’s so feverish she can barely speak, and so is unable to warn Laura of the plot against her. Soon Laura too is feeling faint, though not of natural causes. Countess Fosco has added something to her tea that knocks her unconscious.
Meanwhile, the Count goes in place of Laura to meet Anne at the boathouse. Instead of Anne, he finds the woman who raised her – Anne is too sickly to come. He ingratiates himself and claims he’s a doctor, then offers to bring Anne to London, where he can treat her. She accepts.
The next day when Laura finally regains consciousness – the housekeeper has to sprinkle water on her face to rouse her – the Count, Marian, and all the staff are gone. Sir Percival had sent the housekeeper on an errand, so she’s as confused as Laura. Laura confronts Sir Percival, who says he dismissed the staff because he’s closing up most of the house for a while. While Laura “slept,” Marian made a sudden recovery and decided to join the Count on his trip back to London, with plans to continue on to Limmeridge.
Laura doesn’t believe it, and makes plans to follow Marian. Sir Percival allows her to leave, but insists that she stop in London and stay with the Count on the way to Limmeridge – the journey is too long otherwise. Laura distrusts the Count, and writes to her old caretaker, Mrs. Vesey, asking to stay with her instead. Before she leaves, she tells Sir Percival that she may not ever come back.
Count Fosco is waiting for her at the train station in London. He tells her that Marian is still at his house; he’ll take Laura to see her. But when she arrives there she is met by two men with odd questions: where were you brought up, who is your mother? Confused, she answers. Satisfied, they leave.
Fosco gives Laura a spiked cup of tea, telling her that Marian is asleep. And once again, Laura passes out.
Unsurprisingly, the Count is lying about Marian – she never left Blackwater. The housekeeper hears a noise from a locked room in an unused wing of the estate and finds a lone servant girl tending to a still-feverish Marian. Appalled, the housekeeper immediately goes to Sir Percival and tenders her resignation. He tells her not to pry into his personal affairs; Marian and Laura are both sick in the mind and require unique attention. The housekeeper decides to stay at Blackwater until Marian is well enough to leave, fearing for her health if she is left alone with no one to nurse her.
Therefore, it is the housekeeper who brings Marian the devastating news that Laura has died.
Marian goes to London to meet with her lawyer, Mr. Gilmore, who has suffered a stroke; a colleague is in charge of Laura’s affairs in his stead. He gives Marian a letter: Walter has returned from Honduras.
Marian has the dreadful task of informing Walter of Laura’s death, and, suspicious of the cause, the two return to the lawyer. Marian heard the Count and Sir Percival plotting to kill Laura; surely this is murder. But the coroner said Laura had a weak heart (she didn’t) and died under natural circumstances.
Marian and Walter need another lawyer to investigate the death, but don’t have the funds to pay for one. Walter’s mother suggests they go to Erasmus Nash, a trustworthy friend of Walter’s father. He’s a scrivener (a scribe or notary), not a lawyer, but he’ll do. He agrees to interview all involved witnesses.
Nash is the man we’ve been seeing questioning everyone in flash-forwards. He eventually uncovers a clue: the woman who raised Anne Catherick reveals that Anne’s mother didn’t cheat with any random man: it was Sir Percival. Anne was probably his child, and he and her mother put her in an asylum to keep the secret from coming out.
Marian and Walter need to find Anne; she could tell them more about Sir Percival. They search all the asylums near London, offering bribes for any information. Eventually they find her, but are barred from seeing her: she’s in solitary confinement, not allowed to interact with anyone from the outside world.
Marian sneaks into a gallery where family members can watch from a balcony as the asylum inmates eat. She spots Anne – and realizes that it’s Laura. Anne must have died of illness, and Fosco and Sir Percival passed her body off as Laura’s, putting Laura in the asylum by claiming that she was Anne.
It’s a traumatized and anesthetized Laura, however, as Marian and Walter discover when they bribe an asylum worker to break her out. She has been kept in a strait jacket and pummeled whenever she denied that she was Anne, and the abuse has taken a mental toll. Marian brings Laura to Limmeridge to recover, but Laura’s uncle refuses to admit them, believing Laura is dead. Count Fosco had written, warning that Anne might try to come to Limmeridge and pass herself off as Laura. Despite Marian’s protestations, Mr. Fairlie kicks them out.