DS Ramani de Costa is left to cope with the new Vulnerable Persons Unit which is low on staff while most of the other officers are dealing with a robbery so DCI Jack Meadows assigns DC Terry Perkins to assist Ramani on a case concerning a young man suspected of being a paedophile. Meanwhile it's Lance's stag do and after talking to Sheelagh, Lance decides he's doing the right thing in marrying Mark but in his stag do he goes out to make a phone call and is kidnapped by a group who put a bag over his head and pull him into the back of a van. Phil apologizes to Sam about the prison Liaison officer.