The now famous “Detention Adventure Four” have reached a dead end in solving the mystery of the map they uncovered in the long lost lab of Alexander Graham Bell. Raign, Joy, Hulk and Brett are stumped and frustrated and think they’re done with treasure hunting until they’re framed for an epic prank by the retro-obsessed Kelly, who holds the key to their puzzle. With the group forced to serve their detention under the watchful eye of the local historian Miss Dumont, the gang must dive deep into the muddy history of their town in search of Ignatius Cockshutt’s lost treasure. Along the way their bonds are tested, and they learn that history requires a critical eye to fully understand. Kelly confronts her anxiety disorder, and addresses the tensions that have been straining the group. As the season unfolds, they’re given cryptic encouragement by Principal Lounsberry and the mysterious antique shop owner Gregor, who celebrate their triumph by offering them a clue to solve a new mystery: a lost painting by Group of Seven artist, Lawren Harris.