On Scotland's treacherous River Clyde, three tugboats and a massive bulk carrier are blinded by fog during a 17-mile journey from Greenock to Glasgow. When one tugboat is apparently grounded, the other tugs carefully guide the cargo ship safely to its destination...but their relief will be short-lived. Witness the 2007 sinking of the Flying Phantom and follow the Marine Accident Investigation Branch as they race to discover if the disaster was cause by a collision, human error, or by a malfunction that may put other tugboat crews in danger?