Jack is the middle son of Strike’s sister, Lucy.1 According to Lucy, Jack “hero worships” Strike2 and wants to be a soldier like his uncle.3 We first meet Jack in The Cuckoo’s Calling when Strike attends Jack’s birthday party. Jack finds Strike in a room alone where he opens the soldier figure Strike bought for him. Lucy later finds them playing with the soldier, with Jack pretending to shoot Strike and Strike pretending to have been shot in the stomach.4

In Lethal White, Jack becomes ill with a bad case of appendicitis. With his parents gone on an anniversary trip to Rome, Strike stays with Jack in the hospital until his sister and brother-in-law are able to return. Accompanied by Robin, Strike is clearly upset by the state of his nephew and resolves to become a more involved uncle.5   

Due to Joan’s illness in Troubled Blood, Strike is able to spend more time with his favorite nephew, Jack.6 “‘I like Jack,’ said Strike, with what appeared to be surprise. ‘We’re interested in the same stuff.’” 7

In The Ink Black Heart we learn that Strike still has a soft spot for the now twelve-year-old Jack. They have continued to go on days out together, and now that Jack has a mobile phone ‘they texted each other jokes or information they thought the other might appreciate.’ (Ch 32) Strike tapes a copy of Jack’s homework report on the Battle of Neuve Chappelle to his kitchen cupboards. (Ch 43)

1: The Cuckoo’s Calling, Part 3, Chapter 2
2: Career of Evil, Chapter 30
3: The Silkworm, Chapter 15
4: The Cuckoo’s Calling, Part 3, Chapter 2
5: Lethal White, Chapter 26
6: Troubled Blood, Chapters 2,4, 44, 54
7: Troubled Blood, Chapter 7