The Mitchell family catch troubled teen Ace, red-handed, as he spray paints one of the zoo's giant turtles. But the reptile keeper decides to give him a chance and Ace finds, to everyone's surprise, that he truly enjoys caring for reptiles. He is taken in by the Mitchell family and earns the respect of the two Mitchell children, Susie and Nick.

Meanwhile, the irascible Col Archibald Spencer does his own detective work and wrongly accuses young Tim Watson of harming the turtle and putting a stumpy-tailed lizard in Mrs Spencer's handbag.

More by fortune than design, Col Spencer eventually tracks down the correct culprit and uses his influence as the zoo's primary benefactor to insist on redressing the crime. To the dismay of zoo vet Dr David Mitchell, zoo director Ken Bennett has his hand forced by Spencer and has to fire Ace.

However, the episode ends with Ace promised a job at Taronga Zoo in Sydney and heading north on the train.