S5·E7 UXB

Colin discovers an unexploded bomb in the basement and tries to warn Gordon, who doesn't listen and tells Colin to sort it out. Gordon is preparing to depart for Brussels, though Helen isn't so keen - until she sees how well they'll be living. Colin is sent to hospital after being hit on the head by a croquet ball, leaving the staff celebrating their positive futures, oblivious to the danger in their midst.