The film follows Charles (Tim Key), an eccentric lottery winner who lives a lonely, reclusive life on the remote Wallis Island (filmed in Pembrokeshire, Wales). His fantasy is to reunite his favourite folk music duo, Mortimer-McGwyer, who were also former lovers, for a private concert on his island.

The bandmates, Nell Mortimer (Carey Mulligan) and Herb McGwyer (Tom Basden), accept his invitation, but their reunion on the island causes old tensions and unresolved feelings to resurface. The film is a quiet, character-driven story that blends dry humour with deep emotion as Charles desperately tries to salvage his dream gig.

Run time 1 hour 40 minutes