It's one of the most memorable unsolved crimes from 2012. A British family from a quiet suburban village on a caravanning holiday near Annecy in the French Alps, gunned down in broad daylight. Miraculously, the family's two young daughters survived.
The investigation into the apparently motiveless killings of three members of the Al-Hilli family and French cyclist Sylvan Mollier has involved British, French, Swiss, Swedish and Spanish agencies.
But with no obvious motives behind the killings, conspiracy theories and speculation have run riot, linking the victims with religious extremism, espionage and secret services.
There are rumours of secret Swiss bank accounts, inheritance disputes, French heiresses and bloody family feuds.
Eight months after the killings, there are no suspects, there have been no arrests and the investigation appears to have stalled.
This programme goes behind the headlines and puts the speculation to the test.
It features the only interview with the hiker who saw the crime scene and helped raise the alarm. A French journalist reveals that he has had sight of a confidential police report about the forensics of the crime scene.
The programme features an exclusive interview with a close friend of the Al-Hilli family and his extraordinary email exchange with his friend Saad Al-Hilli. And Dario Zanni, the Swiss prosecutor, is interviewed for the first time about the case.