In the Outer Hebrides of Scotland, a man washes up on a deserted beach with no knowledge of who he is or how he got there. At a remote, sea-battered lighthouse on a rock in the northern Atlantic, homicide detective George Gunn investigates a brutal murder. And in an Edinburgh bedroom, teenage Karen Fleming cannot accept that her scientist father committed suicide. The three incidents begin to converge on a desolate, ancient path called the Coffin Road.