Murphy's Law

- Season 4

(2006)

A vicious and unprovoked race attack lures a reluctant Murphy back to the murky and dangerous world of undercover policing after taking compassionate leave to care for his ailing mother. All evidence points to the notorious Johnstone brothers, exiled from Belfast now operating in Leicester, and leaving a trail of destruction in their wake.

Billy Johnstone blows Tommy Murphy's cover when he lands a copy of the CPS report, and decides to pay him a visit at his mother's nursing home in Belfast. Once there, a fight ensues and the pair are arrested, leaving the detective with no choice but to persuade Billy to become an informant and reveal information about his brother Drew Johnstone's work with Mo Khan.

Billy Johnstone and Murphy return to England in time for Billy's brother Drew's wedding, where the detective hopes his informant will be able to gain the necessary information to bring down Mo and Drew. However, before the big day Billy learns about his brother's plans for the future, leaving him overwhelmed with anger. A shootout between the Johnstones and Murphy soon takes place putting the cop's physical and emotional health at risk.