Undercover is a cheap B film filler with film noir intentions. Johnny Carpenter, an American journalist in London. He sets out to find why his brother in law, Billy Peters, also a journalist was killed.
Carpenter finds a bunch of gangsters running scams such as extorting people who would be involved in set up accidents after they were drugged and allegedly ran over an elderly gentleman in a drugged state. They are also involved in drug dealing as well.
There is nothing too involving or exciting here. A lot of the scenes have interior settings. There is a pointless photo shoot involving a beautiful model. Author Jackie Collins has an early acting role who plays the sister of Carpenter's girlfriend and is also mixed up with the gangsters.