In order to earn money for a certain charity, PJ comes up with a plan which he explains to his skeptical friends, Matty and Shelly. PJ is a terrific bowler and wants to enter a professional tournament that gives cash prizes. However, being only 14 years old, he's sure the tournament won't accept him to compete against adult professionals. What to do? The boys put their heads together and come up with a plan. PJ will wear a mask, and being big for his age, will easily pass as an adult. The explanation is that this individual, using the alias "e;Senor Mysterioso,"e; must wear a mask because he's a secret government witness against a big mob boss and his identity can't be revealed. All goes according to plan, except that this is such an interesting story - a masked bowler - that it becomes big news all over the country. Several gang bosses, who actually do have trials coming up, see the story and figure that this Senor Mysterioso is a secret witness against them - and each sends thugs to where the tournament is being held to stop this masked Mysterioso in his tracks. What follows is high adventure - with fights and shooting and kidnappings and cases of mistaken identity galore. And while all this is going on, PJ is trying to win a bowling tournament against some of the sneakiest, most brazen competitors that one could ever meet.