When a documentary team comes to Button House to investigate a historical assassination plot, Alison and the ghosts are shocked to discover that it involved one of their own.

A mysterious visitor arrives at Button House with a revelation that leaves Alison reeling. Mike has an epiphany on his first day at a new job, which causes Julian to remember his first day as a ghost.

While Button House is being fumigated for woodworm, Alison and Mike decide to save some money and camp in the grounds, sending the ghosts' routines off kilter.

Alison has invited Lucy to come to Button House for a sleepover, but after a concerning meeting with the solicitor, Alison must work out if Lucy is really who she says she is.

When the ghosts try to sabotage Alison's makeshift therapy session for Kitty, they unwittingly face their own demons. And Mike's desire to see the ghosts yields surprising results

While Alison and Mike gear up to make a big investment, the Captain and Kitty work together with the other ghosts to solve an unfolding mystery before it's too late.