The Day of the Jackal season 1 came to an end with a surprising death on December 12, 2024. Based on Frederick Forsyth’s novel of the same name, the show keeps the viewers on the edge of their seats through 10 captivating episodes.

The Sky Atlantic and Peacock series follows a skilled assassin, going by the code name The Jackal, who goes on a mission that could change his life. However, MI6 agent, Bianca Pullman, makes it her own mission to track him down and expose his identity.

As the cat-and-mouse game between the two goes on, a mole in the intelligence agency helps the Jackcal while putting their own teammates at risk. In The Day of the Jackal season 1 finale, MI6 Deputy Chief of Staff, Isabel Kirby, is revealed to be the mole.

Isabel Kirby is the mole in The Day of the Jackal Season 1

Lia Williams as Isabel Kirby (Image via Peacock)

The Day of the Jackal season 1 finale reveals the identity of the mole as Isabel Kirby, MI6’s Deputy Chief of Staff. Throughout the season, Isabel works closely with Foreign Secretary, Jeremy Whitelock, who is secretly conspiring with Timothy Winthrop, a corrupt financier and the Jackal’s boss.

They work together to cover up the assassination of UDC, a tech genius and activist, and erase any evidence that could lead back to them. Isabel plays an important role in hindering MI6’s investigation into The Jackal, whose real name is Alexander Duggan.

Early in the season, MI6 agent, Bianca, suspects that The Jackal has military training, and her theory is proven right in later episodes. It is revealed that Duggan was once a British Army sniper who faked his death after a mission in Afghanistan went wrong.

Duggan turned against his own squad after witnessing their war crimes. He killed them and disappeared to start a new life. As Bianca reaches closer to the truth, Isabel causes trouble in her investigation, claiming that the case is not right for MI6.

Isabel shuts down the investigation against Duggan in The Day of the Jackal season 1 episode 9. However, she later encourages Bianca to continue pursuing him. This is all part of a plan to eliminate Bianca.

Isabel knows Bianca is determined to trace the Jackal, and would not stop until she finds him. Isabel, Whitelock, and Winthrop see the agent as a threat, and hence, come up with a scheme to kill her.

Why Isabel Kirby betrays MI6 in The Day of the Jackal season 1?

A still from the show (Image via Peacock)

Isabel’s betrayal stems from her loyalty to Whitelock and her desire for power. She is on Winthrop’s payroll and works to protect his interests. Winthrop fears that UDC’s new software would expose his illegal activities, and hires the Jackal to assassinate UDC.

Isabel helps cover up the crime in The Day of the Jackal season 1. By the end of the season, Isabel is promoted to Chief of MI6. However, her lies might be uncovered soon, as Bianca sends a message exposing her to her supervisor, Osita Halcrow, just before her death.

The Day of the Jackal season 1 ends with the Jackal narrowly escaping an attack by Winthrop’s men. When he gets to know about Winthrop’s betrayal, he decides to run away and look after his wife and child.

Meanwhile, Isabel’s promotion and Bianca’s warning to Halcrow leave the future of MI6 in jeopardy. The repercussions of Isabel’s betrayal and actions might be explored in the next season, which has already been ordered by Sky Atlantic and Peacock.

All episodes of The Day of the Jackal season 1 are streaming on Peacock.