Justin is determined to make this summer his best yet. Unfortunately, his plan goes up in flames when his fireworks blow up the boathouse. Everyone blames Justin, but he knows he's innocent. He just has to prove it. Maisy's mother Mimsy shows up to spend her "last" summer with her family. And Billie meets both a gorgeous tree planter and a climate activist who threaten to blow up her summer too.

The Lake tells stories about the Canadian Cottage Experience centered around Justin (35), a recently divorced gay man trying to reconnect with Billie (16), the daughter he gave up for adoption while battling his stepsister Maisy-May for the rights to the family cottage.