Nisha Patel-Nasri was found stabbed to death in her home in 2006. Her husband had a strong alibi, but as police begin to dive into his past they uncover a life of criminality, corruption and organised crime. Robbie Coltrane reveals eight of the hardest, most complex and baffling murder cases ever to be investigated by British police. The focus of each programme is the trail of evidence: how it was discovered, what it meant and how it became critical to crack the case. With interviews from the lead investigators and forensic specialists, many speaking for the first time, Robbie reveals the astonishing twists and turns of often stranger-than-fiction cases. It is a record of the detectives’ art: using skill and determination to solve seemingly unsolvable cases – because the only difference between success and failure is critical evidence.