In June, Clyde receives an affectionate letter from Sondra at Twelfth Lake and a lonely one from Roberta from her home. She is expecting him to come soon, but Clyde is desperate to find a way out of doing so. That evening he reads a news report in the newspaper about a young couple who, it appears, drowned in Pass Lake when their canoe overturned. The body of the woman has been recovered, but not that of the man. Then an idea comes into Clyde’s head: if he and Roberta happened to be in a boat on a lake, and it capsized, that would be the solution to his problems, since he knows Roberta cannot swim. He dismisses the thought, but it soon comes back. He dismisses it again, saying he must never think such a thought again.
Clyde calls Roberta. He is non-committal about his plans but says he is still trying to save some money. Then he goes to Twelfth Lake for the weekend, where he takes part in a whirl of social activities with Sondra and her friends, including tennis, riding, and dancing. He and Sondra embrace and kiss. Sondra says she loves him and will not give him up, even though her mother would be opposed to the match. He suggests that they elope together. Sondra says no, it would be better to wait a few months until she is of age, then she can do what she likes. Clyde is dismayed, and thinks again of the boating accident at the lake.
When Clyde returns to Lycurgus, he finds two letters waiting for him from Roberta. She is miserable and wants to know when he is coming. In the second letter she again pleads with him to come, saying otherwise she will return to Lycurgus. He calls her, saying he will come by July 7 or 8; he needs the extra time to accumulate the money they will need. He promises to call or write every other day, and this mollifies her. After this, Clyde thinks again of murdering Roberta in one of the isolated lakes that he has just visited with his friends.
Clyde begins to plan the murder. He will pretend to agree to marry Roberta, take her to Big Bittern Lake beforehand, register under a false name, rent a boat and capsize it, leaving people to believe that both occupants drowned. Roberta writes to him on June 30 that unless she hears from him within 48 hours, she will come to Lycurgus and reveal the entire situation to everyone. Clyde calls her to forestall this, saying he will meet her on July 6 and they can go on a little trip before they get married. As he talks he plans in his mind the details of the murder.
On July 6 Clyde and Roberta travel separately by train to Utica. Roberta is expecting them to be together for seven or eight months. As he sits on the train, Clyde reviews his plans. He plans to stay one night with her in Utica, then travel to Grass Lake, stay another night, and then go to Big Bittern Lake the following morning. He works out all the details of his plot in his mind.
At Grass Lake, Roberta sees that a religious group is gathered there, and she suggests to Clyde that they get married there and then. Clyde pretends to inquire and tells her that a marriage cannot be arranged at that time. The next day they travel by train to Gun Lodge and then by bus to Big Bittern. Clyde is nervous as he talks to the bus driver. At the inn he signs the register as Clifford Golden and wife. He then rents a rowboat and he and Roberta go out on the lake. They stop in a bay and have the lunch they have brought with them. After that he rows her out on the lake, contemplating what he is about to do. They stop on the shore once more, where Clyde takes some photographs of Roberta. He leaves his bag safe and dry on land, and then rows out to a deserted spot on the lake. But when the crucial moment comes, Clyde is unable to act. A strange expression comes over his face, which alarms Roberta. She gets up to take his hand, but he accidentally hits her in the face with his camera. She falls back, and as he gets up to assist her, the boat capsizes. They are both thrown into the water, and the left side of the boat hits Roberta on the head. Knowing she is drowning, she in desperation calls to Clyde for help. Clyde does nothing to save her and swims to the shore. He buries the tripod for the camera and begins walking south through the woods.
The story moves relentlessly on to its climax. Clyde is helpless to resist the idea that took root in his mind. So intoxicated is her with his plans for marriage to Sondra, that he cannot think clearly. The narrator brings attention to his mental condition at the beginning of chapter XLV, when he says of Clyde, “the mind befuddled to the extent that for the time being, at least, unreason or disorder and mistaken or erroneous counsel would appear to hold against all else.” But ironically, despite all his careful planning (which will later turn out to be not so careful), Clyde’s plan succeeds only, as it were, by accident. At the crucial moment, he loses his nerve. He realizes that he cannot go through with it. Instead, an impulse comes to him simply to say to Roberta at that moment that he will never, under any circumstances, marry her, but he is so paralyzed that he cannot even speak. What follows, if it were not a tragedy, might be considered a comedy of errors. Clyde hits her accidentally with the camera (he had intended, in his planning, to give her a blow that would stun her); and the boat collapses accidentally. He has achieved his original aim in spite of his apparent inability to act. He fails to make any effort to save her, when she is in the water, but is Clyde in fact of guilty of murder? This is what the next book will set out to examine.