Chapter summary
3 DECEMBER - 13 HOURS, 50 MINUTES UNTIL DAWN
Mark spends the late afternoon buried in the enormous 50/50 Killer file, taking coffee breaks with Mercer. While reviewing the file he receives a buzzing text from his parents asking him to call, decides not to reply, and puts the phone back. He notes two sets of fingerprints in Kevin Simpson’s house—Simpson’s and an unknown set that might belong to a woman named Jodie. The door‑to‑door canvassing team yields few leads. Greg calls in an IT update: six grainy CCTV stills of white vans captured near Simpson’s house the morning the killer would have left. The vans are enhanced and identified, but names and addresses are still pending. Mercer redirects the canvassing crew to follow up on the vans and orders full video and audio capture.
Mercer then shows Mark the CCTV footage of Detective Andrew Dyson’s final moments. The clip, recorded from a lamp‑post, shows Dyson arriving at a suburban house at 14:13, ringing the bell, entering a slightly ajar door, and disappearing inside. The narration describes the house’s bland red‑brick façade, driveway, garage, and untended garden. The file explains that Dyson was investigating a supposed “Frank Walker,” a fabricated identity used by the killer. The killer attacked Dyson with two long, thin‑bladed knives, delivering six clean stab wounds in two clusters (front and side), then cleaned the scene and fled on foot, leaving no vehicle trace. Dyson’s body was found three hours later, bound in the living room. The investigation later proved that Frank Walker never existed; the name and the empty house were a ghost cover for the killer’s movements.
Throughout, Mercer makes numerous calls to DI Alan White, keeps internal notes, and appears mentally exhausted. He hints at his own fatigue, offers Mark a half‑hour break, and tells him to get coffee from the canteen while Mercer continues to hold the fort.