The plot of The Big Top Secret involves finding lost friends and the joy of forming new friendships. Briar's life drastically changes when he gets taken from his comfortable home and brought to a struggling circus run by Hugo the Gorilla. Briar, who is frustrated with his brother Bramble and forest friends, discovers a new family and acceptance at Wolfgang's Big Top. With Briar's help, the circus regains its energy and Briar flourishes in his newfound fame and companionship. However, Briar's happiness gets complicated when Bramble and his forest friends finally show up, and Briar is forced to choose between his new life and his old. Throughout the story, all the animals learn the importance of belonging and develop a deeper understanding of kinship through a series of challenges, adventures, and train rides.