It's summertime again, and we join the 12-year-olds of Camp Average--er, Avalon--as the season is winding to a close. Last year, our favourite junior campers (including Andre, Mack, Nelson, and Miles) won the big baseball tournament, so this year, the camp has established a special competitive stream for elite athletes. Camp director Winston even opened up space for girls--so Makayla, Nicole and friends are on board too. And best of all, Mack can happily get back to his usual: spending time at the waterfront with not a care in the world. Leave it to dastardly Winston to ruin his fun. When the camp director takes a special interest in the basketball team, and enters them in the Swish City 5-on-5--Camp Average's one last chance to win a trophy--Mack smells a rat. He certainly won't be joining... but it starts to feel like he doesn't have a choice, as one by one, activities all over camp are supposedly closed for repairs and maintenance. Winston seems up to his own tricks, pitting camper against camper (in this case, boys against girls) in a twisted attempt to wring a winning performance from his charges. In an attempt to undermine Winton's scheme, Mack creates a scheme of his own, in which he must secretly sabotage both the boys' and girls' teams. Will Mack match wits with Wintston and save the camp from the diabolical director's clutches once and for all? Or will Mack's own skullduggery be exposed--and lose him his summer and his friends?