This episode follows the work of a specialist rape unit in Portsmouth, the first dedicated unit to be established outside London; in other parts of the country rape is bundled in with other crimes and conviction rates can be as low as five per cent. Rape is a uniquely difficult crime to solve. It often takes place behind closed doors with no corroborating evidence, and no outside witnesses: all too often it boils down to one person's word against another's. Can Crystal - a unit of dedicated officers - make a difference?