Two lives. One house. A hundred postcards.

When Ava and Will first meet at university, sparks do not fly. But as her best friend's boyfriend, they end up in each other's lives, living under the same roof. Their landlady explains that there has been a tradition at 23 Ivy Lane since she was a girl - if you're ever away from home, you always send a postcard back, sharing your adventures. Their student pinboard fills with their memories from Glastonbury, European summers and student exchange visits.

As graduation - and real life - approaches, both Ava and Will dread leaving the house they've called home. So, when their landlady falls ill, they immediately chip in what they have to buy it from her cheaply, under the promise that they'll keep up the tradition as housemates.

Over the years and decades that follow, and the loves gained and lost, life takes Ava and Will to many unexpected places. Postcards always arrive at 23 Ivy Lane - some hopeful, joyful, tragic, regretful. With each rattle of the letter box, they begin to wonder, after all, isn't home really where your heart is?