Dragon Quest Monsters: Joker review at Gamepro.

"In Dragon Quest Monsters: Joker, you play as a young man with an enormous chip on his shoulder--though it's understandable considering that in his case, being grounded means being hurled in a dungeon for ten days.

His father, Warden Trump (a shoo-in for Father of the Year), releases you on the condition that you participate in the Monster Scout Challenge as an agent of the mysterious CELL organization--meaning he probably wants to get his hands on the prized Scout's Mark. And thus, you're effectively been launched into your monster-collecting adventure."

Full Source: Gamepro