The Mysterious Benedict Society and The Perilous Journey by Trenton Lee Stewart

For the second time, Kate, Reynie, Sticky, and Constance are joined together by Mr.Benedict. This time, he has prepared them a scavenger hunt to test their talents. But before they start off, Rhonda gives them bad news; Mr.Benedict and Number Two have gone missing and it has to do with the horrible Mr.Curtain! As they follow the clues to try and save Mr.Bendedict and Number Two, they face Mr.Curtain's new helpers; Ten Men who have ten different ways to hurt you. Here's a part in the beginning:

"What if we come across a Ten Man?" Constance asked. "Don't worry about that," said Kate, with a dismissive wave of her hand. "We'll just need to keep an eye out for suits and briefcases-and, you know, be prepared to run for our lives." "Thank you," said Constance with a quaver in her voice. "That's ever so comforting." "A Ten Man probably wouldn't even notice us,"Reynie said. "Four children don't exactly look like a rescue team, you know." "Well, I suppose that's true," Constance said in a somewhat stronger voice, and Reynie smiled encouragely. He didn't quite believe what he'd just said-he suspected at least some of Mr.Curtain's henchmen would have heard about them. But Mr.Curtain, of all people, would hate to admit he'd been outsmarted by children, and it was possible he'd avoided mention of them. At any rate, Reynie thought it best to shore up Constance's courage, for he could tell she intended to come along regardless. Kate cracked her knuckles. "If we're going to do this we need to get started. Four days, the letter said, and we may need every minute." "So, what's the plan?" Sticky asked, putting away his polishing cloth and resetting his spectacles. If we're in agreement," Reynie said, "We'll go wherever these instructions lead us. Secretly, of course. The adults would never let us go now-not even if Rhonda and Milligan came with us." "Of course not," said Kate.
"we'll need to sneak out." "oh boy," said Sticky, who hadn't thought about this yet. "If a Ten Man doesn't kill me, my parents surely will." Reynie grimaced, imagining how Miss Perumal would react when she discovered he'd gone. He quickly forced the image out of his mind. "are we agreed, then" Kate asked. "Agreed" said Constance and Reynie. Sticky let out a breath. "Agreed." Everyone looked at the envelope then, wondering where in the world-and into what unknown dangers-it was to take them.

I loved this book a lot; more than the first one. This book has adventure, bravery, friendship all in one.