Percy Jackson: Sea of Monsters Logan Lerman, Alexandra Daddario, Douglas Smith. Directed by Thor Freudenthal. Rated PG. Now playing.

WhenPercy Jackson & the Olympians: The Lightning Thief was released in 2010, it was positioned as the potential heir to the Harry Potter franchise, with a popular fantasy book series as its source and the director of the first two Harry Potter movies (Chris Columbus) behind the camera. Three years later, sequel Percy Jackson: Sea of Monsters gets scaled-down promotional efforts and the director of Hotel for Dogs.That’s probably for the best: This is a thoroughly second-rate franchise, and its latest installment features a rote storyline about teen demigod Percy (Logan Lerman) and his friends on a quest to find the mythical golden fleece and save the world.

The special effects are adequate, the life lessons are family-friendly, and the characters are blandly likable. The Percy Jackson series is never going to be the next Harry Potter, but with movies like Sea of Monsters, it can probably continue in acceptable mediocrity for years to come.