Stuck in the desert with a drug lord in their car boot, Barnaby and Nina are in a real mess. The pair are even more worried when they learn that the Sherman twins have put a price on their heads.

Barnaby and Nina need to escape Mexico. But with a price on their heads, the only way is to pose as man and wife. What could go wrong?

Having made it back to England, Nina is desperate to get home to her family. She's out of options - until the Shermans offer her a reward for finding the Hitler painting. But Barnaby wants no part of it. So now Nina has to choose between Barnaby and the money.

Barnaby has been taken prisoner by Colin McQueen, who is also looking for the Hitler painting. Nina and Leah will have to work together to find the picture and free Barnaby while trying to keep the Sherman Twins' bounty hunter at bay.

When McQueen discovers the painting he has been given is fake, a gun fight ensues at Barnaby and Nina's wedding, arranged to allow a safe place for the hostage/painting exchange. As the dust settles, Barnaby realises what true friendship really is and Nina claims her bounty from the Sherman Twins.