Option Lock is an original novel written by Justin Richards and based on the long-running British science fiction television series Doctor Who. It features the Eighth Doctor and Sam.

The Doctor and Sam land in present-day England on the ancestral home of the Silver family. However, the house holds clues to a dangerous centuries-old society and something that drove a man to suicide. Unravelling this will take Sam and the Doctor through time and space to save Earth from nuclear fire.

• Option Lock title listing at the Internet Speculative Fiction Database