Pathfinder Adventure Path #151: The Show Must Go On - Rules of Play says:

"The Show Must Go On" is a Pathfinder Second Edition adventure for four 1st-level characters. This adventure begins the Extinction Curse Adventure Path, a six-part, monthly campaign in which the heroes lead a traveling circus as they unravel a plot to eradicate all life from the Starstone Isles at the heart of the Inner Sea. The adventure also includes advice on how to run a traveling circus, new circus-themed rules, and a menagerie of monsters both wondrous and wicked.