Salt is set on the East Norfolk coast in 1770, where the harsh rhythms of the sea shape a world steeped in superstition and brutality. Man Billy, a volatile young fisherman, lives isolated among the dunes with his controlling mother, Widow Pruttock. Their existence is governed by fear, belief, and the relentless pull of the ocean.

The arrival of Sheldis, a traveling singer rumored to possess otherworldly powers, disrupts this fragile balance. As Billy becomes increasingly obsessed with her, his mother grows convinced that her son has been enchanted. Determined to protect him and preserve control, she is driven to extreme measures to sever the bond she believes is cursed.