Seamus Callahan in With a Vengeance: Accomplice, Killer, Martyr

Overview

Seamus Callahan is one of the most complex figures in Riley Sager’s With a Vengeance. Introduced as Anna Matheson’s quiet, loyal accomplice, he is revealed over the course of the night to be a secret murderer acting on his own violent code. Beneath the surface of a grief-stricken brother lies a man with a terminal nerve condition, a hidden cache of pills, and a thirst for blood that Anna never fully anticipated. His arc moves from helper to hunter to sacrificial martyr, making him both a perpetrator and a victim of the story’s brutal logic.

Plot Role and Key Actions

Seamus’s primary role is that of Anna’s co-conspirator. He first approaches her at her aunt’s funeral, bearing six boxes of evidence that prove Anna’s father was framed for the train explosion. Together they spend a year planning to trap the six people responsible. On the train itself, Seamus poses as a fake conductor, helping Anna keep the passengers contained.

But Seamus goes rogue. Without Anna’s knowledge, he murders Judd Dodge (smothering him and staging the body), kills Edith Gerhardt later in the same manner, and attempts to murder Jack Lapsford with a pillow before Anna catches him. He also carries a revolver that he later loses, and his gunshot is heard after he leaves to “check the observation car.” His final act is to confess to Anna, return her father’s lapel pin, and jump from the train onto a bridge—a last, deliberate leap into death.

Motivations and Character Traits

Seamus’s surface motivation is the same as Anna’s: revenge for the deaths of his brother Sean and Anna’s family. But his deeper drive is far darker. The retrieved evidence shows that when Anna first asked “Do you think we should kill them?” Seamus answered “Yes. All of them need to die. And I want to be the one to do it.” Anna’s desire for legal justice could not satisfy his need for direct, violent retribution.

His secret terminal nerve condition (manifested as a severe tremor in his hands, which he tries to hide) gives him a desperate, fatalistic edge. He knows he has no future, and this knowledge frees him from moral restraint. The pillbox he carries—originally containing six pills, then five after he used one—confirms he had access to poison, though the murders are committed by smothering.

Seamus is loyal to the point of self-abnegation. He defers to Anna in every decision, saying he does so because she lost more family than he did. Yet that same deference enables his double life. He tells her “I’m sorry you were never supposed to know” when she discovers him trying to kill Lapsford. He is secretive, protective, and ultimately self-destructive. Killing, he admits, felt “beautiful,” but he also says he has “killed enough” and stops only when caught.

Chronological Arc

1. Before the novel: Meets Anna at her aunt’s funeral. Has served in the Army, following his brother Sean. Suffers from a progressive nerve condition that worsens over time.
2. Planning stage: Works with Anna for a year to assemble evidence and design the train trap. They repeatedly discuss killing the conspirators, but Anna settles on exposing them.
3. Boarding the train: Seamus poses as a conductor, luring passengers into Anna’s scheme.
4. First murder (Judd Dodge): Kills Judd early in the journey, before Anna’s plan to expose everyone even fully unfolds.
5. Second murder (Edith Gerhardt): Smothers Edith in her room, leading to the revelation that a killer is among them.
6. Attempted third murder (Jack Lapsford): Anna catches Seamus pressing a pillow over Lapsford’s face.
7. Confession and flight: Admits everything to Anna in the baggage car. He claims he is “already doomed,” returns the pin, and jumps from the train, leaving Anna holding his revolver.

Relationships

Anna Matheson

This is the central relationship of the book. Seamus and Anna share an unusual bond formed through mutual loss. He is in love with her, but Anna does not reciprocate romantically; their one attempt at intimacy was “too sad,” as he acknowledged. Nevertheless, he remains fiercely loyal, deferring to her in all planning. The betrayal is devastating for Anna, who says she will never forgive him. Though she does not love him the same way, she does care deeply, and his death leaves a void.

Sean Callahan (brother)

Sean was Seamus’s “north star”—his big brother whom he idolized and emulated. After Sean’s death in the train explosion, Seamus lost direction until he found Anna. His revenge is entirely for Sean.

The Victims (Judd, Edith, Herb, Lapsford)

Seamus sees them not as people but as embodiments of the injustice that destroyed his brother. He kills Judd and Edith without hesitation; he attempts Lapsford because Anna’s plan to let them die naturally (by withholding the pill) was not enough.

Kenneth Wentworth

While Seamus never confronts Wentworth directly, his final act—giving Anna the gun and telling her “You can end this”—enables her to kill the mastermind.

Key Decisions and Consequences

Themes and Symbol Connections

• Revenge vs. Justice: Seamus embodies pure revenge, while Anna initially represents justice. His actions show that revenge is uncontainable and leads to more death.
• Betrayal and Deception: He deceives Anna, the passengers, and Reggie. His disguise as a conductor is literal, but his deeper deception is the secret of his killings.
• Guilt and Redemption: Seamus feels guilt only insofar as he betrayed Anna. He does not regret the murders themselves. His jump is not redemption but escape—though Anna might see it as a perverse gift.
• Family Secrets: Just as Anna’s family had secrets (Tommy’s true parentage), Seamus hides his condition and his murderous intent. The Callahans’ unhappy childhood is a secret he carries.
• Survival: Seamus does not believe he will survive; his condition makes survival impossible. He treats the train journey as a last stand.

The trembling hands and pillbox are potent symbols. The trembling reveals his mortality; the pillbox contains both literal poison and the moral poison of his secret killings. The silver locomotive pin (which he returns to Anna) connects him to her father’s legacy—a legacy he tries to reclaim by killing those who destroyed it.

Five Book-Specific Questions and Answers

1. Why does Seamus decide to kill the passengers when Anna only wanted to expose them?
Seamus felt that Anna’s plan for legal justice was too slow and easy. He wanted to be the one to inflict suffering, and his terminal condition gave him nothing to lose. He tells her that killing felt “beautiful” and that he sought the “sweetest release.”

2. How does Seamus hide his nerve condition from Anna and others?
He conceals his trembling hand by keeping it in his pocket, avoiding tasks that require fine motor control. He also uses a pillbox for his condition but never reveals its purpose. Even when he checks Judd’s pulse, he fears everyone noticed his shaking.

3. Why does Seamus jump off the train instead of facing arrest?
He believes he has no future because of his terminal illness. Jumping allows him to control his own death, spare Anna the difficulty of turning him in, and serve as a final act of agency—he “leaves” rather than being taken.

4. What is the significance of Seamus returning Anna’s father’s pin before jumping?
The pin represents Anna’s family legacy and her father’s innocence. By returning it, Seamus symbolically releases her from the quest for revenge and acknowledges that his actions have betrayed that legacy. It is his way of saying she can now end the cycle.

5. Could Seamus have been stopped if Anna had known about his condition earlier?
Possibly. Anna’s bond with Seamus was built on shared grief. If she had understood his desperation and literal doom, she might have challenged his plans more forcefully. But his secrecy and her own single-minded focus on the larger plot prevented her from seeing the signs—until it was too late.

For a deeper look at the story’s ending and Seamus’s ultimate fate, see the ending explained page. For more on the novel’s moral questions, visit the themes section. To explore other characters and plot points, refer to questions and answers.