Code 404

When a scientist goes missing, DI John Major and DI Roy Carver must reignite their friendship.

After visiting an informant in prison, Major and Carver re-examine an infamous cold case which opens old wounds for Major. Carver sees Major's malfunctioning is getting worse and turns to Dr. Parfit for help. Instead, she breaks the bad news. Major has until Pancake Day before his A.I. shuts down. It falls to Carver to protect his partner by keeping him calm while Dr. Parfit searches for a fix. But as the cold case heats up, Kelly goes undercover to get Major to give her a divorce, causing Major and Carver to come to blows.

DCS Dennett officially reopens of the Chelsea Bridge case, reuniting Major with his absent father, Clifford, who failed to solve the case twenty years before. Choosing to hide his A.I. status from his disapproving dad, Major's A.I. grows more unstable and Dr. Parfit and Carver clash over the solution. After a failed family reunion with Clifford, Kelly and Carver, Major joins an illegal fight club to impress his dad, while SIU suffers an embarrassing setback in the Chelsea Bridge case.

Major's A.I. is glitching, seriously impacting his police work. But instead of fixing Major, Dr. Parfit creates a new replacement A.I. for SIU and Dennett realises she only really needs one of them. Kelly thinks she's found a lead in the Chelsea Bridge case, but Carver hasn't got time for her theories now Major's place in the department is being seriously threatened. But when an old friend is brought in for questioning, a trail of corruption leads back to the heart of SIU.

Pancake Day. Carver rescues a dangerously unstable Major from the brink, for now. Dennett calls in a favour from Millikan Biotech, but her attempt to save Major backfires, leaving an unsuspecting Major still in mortal danger and Carver wracked with guilt. When Major and Carver are assigned a witness protection case of some familiar faces, Carver learns some shocking truths and confronts Major. As the fragile partnership is once again torn apart, a desperate Carver turns to Kelly, while Major discovers he has only hours left to live.

With just three hours left to live, Carver and Kelly find a collapsed Major and try to get him to accept the truth. But Major is determined to solve Chelsea Bridge and exonerate his dad before his A.I. shuts down and he dies. When Major's sting operation goes horribly wrong, Carver and Major become trapped in harm's way, while Kelly, Dr. Parfit, and Dennett attempt to track them down before it's too late.