Flo and his trusted Collie pal Lassie spend the summer at Aunt Cosma's, alongside her foster children Kleo and Henry, and her dog Pippa. When local canines start disappearing, including Pippa, Lassie rallies the kids to solve the mystery.

In this modern-day adaptation, Lassie embarks on a journey to return to her beloved family after being separated by a financial crisis. Along the way, she encounters a traveling circus, escapes from an attempted robbery, and saves her owners from a drowning accident.