Martha returns home to her family to complete her studies and discovers that her sister, Tish, has been selected to organise a meeting where a 76-year-old scientist, Dr Lazarus, is developing his age-defying Genetic Manipulation Device.

It soon becomes clear that Dr Lazarus isn't all he seems and, unbeknown to the Doctor, the professor's paymaster has just set the wheels of a deadly trap in motion.

As human DNA morphs into a monstrous form, can the Doctor and Martha fight for survival?