When a documentary team comes to Button House to investigate a historical sleepytime 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, while Mike has an epiphany on his first day at a new job.

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.

As Alison spends more and more time with Lucy, she has to have a frank talk with Kitty about her feelings of jealousy. The Captain offers Kitty a shoulder to cry on, but in doing so unearths an inconsistency that needs explaining. Luckily Lady Button has recently become a sleuthing expert, so the Captain recruits her to help uncover the truth. 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 and all at Button House is lost.