The engines are hard at work to build a new Search and Rescue Center. When Thomas helps a friend in need, he is rewarded with an exciting trip to the mainland. Along the way, he gets lost at sea and finds himself on the mysterious Misty Island, where he meets new friends Bash, Dash and Ferdinand. Together they discover secret hideouts and try to help Thomas find his way home. Will Sir Topham Hatt's search party ever find Thomas?