Too Clever By Half - S11.E100

Carver goes undercover as a barman to expose an extortion racket, where the owner of a pub is being blackmailed into handing over cash in order to prevent any trouble. However, the operation nearly goes awry when an unknowing Beech arrives at the pub to meet with one of his informants. When Carver's cover is blown, Beech becomes prime suspect for giving the nod to the gang – until CID discover the landlord's wife has been in bed with the gang leader.