A gunman opens fire on a bus in San Francisco, killing several passengers, including Detective Dave Evans. Detective Jake Martin, a seasoned officer and Evans' partner, is assigned the task of solving the gruesome crime. Consumed by grief and a burning need to find justice, Martin discovers that Evans had been secretly investigating an old unsolved case involving a prostitute's murder. Partnering with the brash and younger Inspector Leo Larsen, Martin delves into the seedy underbelly of the city to follow leads that Evans had left behind.

As Martin and Larsen navigate through a web of false leads, dead-end clues, and elusive witnesses, they encounter dangerous individuals, corrupt motives, and bureaucratic hindrances. Their investigation reveals startling connections between the bus massacre and Evans’ confidential inquiries. Amidst mounting tension and personal conflicts, Martin becomes increasingly desperate to catch the killer. The pursuit takes them deep into the darker side of human nature and forces them to confront their own vulnerabilities. The stakes intensify as they close in on the truth, risking everything to bring a ruthless murderer to justice.