With exclusive access to crime scene evidence, Retired Detective Inspector Pat Marry relives his four year long murder investigation that put Mary Gough's killer behind bars, and set Pat on course to being one of An Garda Siochana’s leading investigators.

After a decomposed body is found in Galway, a small team of Garda investigators takes on the biggest challenge of their careers, as they use cutting-edge forensic science to identify the remains and uncover the man’s story.

Michael O'Sullivan reveals how he became Ireland's first undercover detective, fighting to smash Ireland's first ring of heroin dealers.