The irrepressible Mim celebrates turning 70 by writing a bucket list. Her reserved daughter Fran tries to make the effort, but new starts and openness are easier said than done.

Mim has a plan to fund her bucket list by selling the contents of a time capsule buried at her alma mater, Cambridge, but instead Fran learns a secret about Mim's past.

It's the night before cousin Pat's daughter Gemma's wedding. When she reveals she doesn't want to go through with it, Mim and Fran try to help her, making some important discoveries in the process.

Mim lets slip a crushing deception, and Fran calls an end to the trip, but it looks like time might be running out for Mim to tell Fran the biggest secret of all.