put a bag over his head and jumped into the river

To take down South Boston's Irish Mafia, the police send in one of their own to infiltrate the underworld, not realizing the syndicate has done likewise. While an undercover cop curries favor with the mob kingpin, a career criminal rises through the police ranks. But both sides soon discover there's a mole among them.

When Cole returns to Yang's haunted temple to seek revenge on a former Airjitzu Master, he accidentally uses a powerful Dark Magic blade that unleashes the spectral forms of Ninjago's greatest villains and traps himself in the temple. The Ninja must return the ghosts to the Departed Realm before it's too late.