July 1966. World Cup fever grips the nation, as Argentina face off against England in the quarterfinals. In a sleepy corner of an Oxford museum, a septet of schoolgirls saunters through the worldly exhibits. But in a closed--off enclave, a blade slashes, blood sprays crimson and a man falls to his death... DC Endeavour Morse is one of the first on the scene in the killing of Adrian Weiss, an elderly gentleman with a specialism in heraldry and genealogy. His throat laid open, Weiss was slain by a katar -- a ceremonial dagger with links to nineteenth century British India. The weapon will prove key to unlocking Weiss' final hours. The mystery propels Endeavour to
the Blythe Mount School for Girls; an establishment isolated in the summer months save for a skeleton staff and a handful of pupils. A
funereal pall hanging over the school stokes the young detective's sense of dread. He returns home to find an instruction ('SAVE ME')
slipped into his coat pocket. Endeavour digs into the building's troubled history, determining a connection between Weiss' untimely fate
and a series of murders on the Blythe Mount grounds. Murders that transpired almost a hundred years ago to the day ---- and presently
unsolved. Tensions teeter over a knife--edge when one of the seven girls disappears into the night, without trace or explanation.
As the centenary of the murders loom and the malign presence within the school quickens its pace, with devastating consequences, Endeavour must retrace the hanging threads of Weiss' remaining research. Spectres from the past threaten to crash into the present and the bounds of the young detective's rational mind are tested.