Set in World War II, Angel of Baker Street is the story of Olivia Drummond who is recruited by Special Operations Executive to be an undercover agent in occupied France. With the codename of Angelique she is sent to Paris to find out what has happened to the Prosper circuit. It soon becomes clear the circuit has been compromised by a double agent.
It is in Paris that Olivia meets Louis Tillon, a former member of the circuit and Eric Kleist, a German officer. Two men who become an integral part of her life as a spy.
Olivia is sent on her second mission but this time to the Auvergne region where, with the help of Louis, she trains the Maquis in their fight against the Germans. Eventually captured, she is sent back to Paris and tortured by the SD. Despite the unbearable brutality, Olivia is determined to survive if only to find and kill the man who she now knows betrayed her.