The 39 Clues Wiki
The 39 Clues Wiki

Luke Cahill is the first child and son of Gideon and Olivia Cahill's five children, and the founder of the Lucian Branch.


Born in 1484, Luke Cahill was the oldest of the five Cahill siblings. His father gave him a portion of his master serum that enhanced his strategic skills. Luke, however, was not satisfied with this, and desired the entire serum. Just before the fire, he tried to convince Gideon to give him all the Clues needed for the formula, but he refused.

Though he rescued them from the fire, Luke's siblings blamed him for it and the death of their father. He became embittered against them and desired revenge. After he left Ireland, he joined King Henry VIII's court in England as the king's advisor. Courtly life taught him that nothing was out of reach as long as one was willing to use bribery, blackmail, and other forms of "persuasion." Luke began to send spies to track his siblings, telling them to do whatever it takes to find their Clues.

Before he went to London, there was a rumor that he had a diary containing what he knew, including what really happened at the fire. It is said that he gave it to someone he thought would be a good idea to trust; his sister, Jane. She hid it in an unknown location for a reason not explained in the books. Luke was the only one of the other four siblings that Jane got along with on occasion. He is the only sibling known to have confrontations directly with Damien Vesper and Madeleine Cahill.


"Revenge above all"


Appearance and Personality[]

Luke Cahill is described as a thin, cruel-looking man with dark (most likely black) hair. He also has deep brown eyes, much like Lucian Ian Kabra. His sister Katherine referred to him as "sneakier than a serpent and even more deadly." He is also said to always be at the wrong place at the wrong time.


Luke at the fire


The Maze of Bones []

He appears on an old Irish portrait in the Paris Catacombs with his siblings.

One False Note []

In Venice, Amy dreams of his portrait back in France.

The Sword Thief []

In The Sword Thief, part of the story of the fire that killed Gideon Cahill, and how Luke and his siblings split apart, is revealed.

Vespers Rising []

Gideon gives all the siblings their serums. Luke immediately takes his portion and in the evening comes to warn his father that Damien Vesper and his men are coming. After rescuing all the siblings he gets blamed for the fire by Katherine and Thomas and leaves to go to London. He later finds Madeleine and appoints her governess for his son, Winthrop Cahill. He eventually attempts to execute her, but she manages to escape.


  • Strategy and planning (effects of the Lucian serum)
  • Cunning
  • Ruthlessness


He does not appear online except on his card when you enter it.



  • He had a dagger found by Sir Isaac Newton.
  • He was the only Cahill child (besides Madeleine) who was certain Lord Vesper set the fire. It has been theorized that Jane believed this as well, due to her love and trust of Luke.
  • He and his mother are the only Cahills to speak directly to Madeleine Cahill and Damien Vesper.
  • He was the only Cahill child who was with Gideon for some time before his death.