Arden Constabulary's inundated with complaints about con-artists doing the rounds - and there's something familiar about the duo. At HQ, Frank and Lu haven't had any new clients in over a week, although Sebastian's inundated with complaints.

Relieved to finally have a client, Frank and Lu visit Emelia Merchant about her missing husband, but she seems to think they've met before... After being turfed out by angry son Ian Merchant, Frank and Lu return to HQ to a furious mob of clients they've never seen demanding their money back, and DI Marlowe waiting with a smug DS Keeler to arrest them on an extensive list of charges, including a theft of £30k.

After a sleepless night in the cells, Frank and Lu set out to prove they're being framed by their mysterious doppelgangers... can the PIs clear their names?