Anna cries briefly, then resolves to act because she believes the true killer is still loose on the train. She clarifies to herself that accusing and restraining Dante Wentworth was a deliberate show to protect him, not because she truly thinks he is the murderer.

Moving through the silent cars, Anna is haunted by the dead—Judd Davis, Edith Gerhardt, and Herb Pulaski—while advancing toward the living compartments. In Car 12, she notices Jack Lapsford’s door quietly closing, indicating someone has just slipped inside without wanting to be seen.

Needing to eavesdrop safely, Anna enters Sal’s room, avoiding looking at Sal’s covered body. She puts her ear to the wall adjoining Lapsford’s compartment and hears Lapsford’s loud demands—“What are you doing here?” and “Answer me, dammit!”—but there is no reply from the intruder.

Concluding the silent visitor intends to kill Lapsford, Anna follows Reginald Davis’s earlier advice to catch the murderer in the act. She bursts from Sal’s room into Lapsford’s, determined to secure justice for Tommy and her parents even at personal risk.

Inside the darkened compartment, with curtains drawn and lights off, Anna sees Lapsford on the bed and a man pressing a pillow over his face. She tackles the assailant, crashes painfully to the floor, and is briefly pinned before the attacker rolls off and stands.

When Anna looks up, she recognizes Seamus Callahan. Seamus bends toward her, offers his hand, and says he is sorry and that she was never supposed to know, implicitly revealing his role in the attempted killing.