Uncle Obadiah leaves Hancock a fortune provided that he gets married. Hancock starts to look for his future wife with the help of the Sid James Marriage Bureau.

Hancock bumps his head and suffers from temporary amnesia. Whilst he is unable to remember who he is, Sid persuades Hancock that he is Prince Nicolai, the last heir to the Russian Royal Family's fortune... but there are others making the same claim.

Sid and Hancock decide to auction off their property to pay for a trip to Monte Carlo to try out Sid's infallible roulette system. But they discover that Hancock's stuffed eagle had been stuffed with banknotes.

Hancock dreams of becoming the great detective 'Sexton Hancock' and proceeds to unravel a complicated murder plot.

Hancock buys a house from Sid but discovers that there's an airfield at the bottom of his garden. Returning to Sid dissatisfied, he is forced to try to sell the house himself but he has considerable difficulties.

Hancock agrees to attend an identity parade at the local Police station. But when he is mistakenly picked out by three witnesses he decides to prove his innocence by recreating the crime.

The TV series is finally over so Hancock and Sid need to get jobs. They take on the role of servants dressed as an elderly couple, but when they take it in turns to be the woman suspicions are aroused.

Hancock takes out a murder mystery book from the library. When he discovers that the last page is missing he is determined to deduce who the killer is. But when he finds that it's too complicated to decipher he decides to track down a copy of the complete book.