 With the aid of his West Indian friend Marvin (Lawrie Mark) and the famous Professor Hercules' body-building course, Sammy is training for the long distance running championship.Two bullies, Sammy's rivals in the race, throw his 'lucky' Tiger T-shirt through the window of a research laboratory.In trying to get it back, Sammy upsets some electrical apparatus and in the resultant explosion the T-shirt is transformed into a source of tremendous power.