Nick and Ava have become friends over the fact that they're the only upper classmen who still ride the bus to school. And every day, they see the same boy - who they call The Kid - walking along the train tracks, even when the weather is terrible or when he's clearly fighting a bad cold.
When Nick notices the mysterious boy practically sprinting along the tracks one day and he doesn't show up the next, Nick and Ava begin to wonder if something might be wrong. But how can they help when they don't even know who The Kid is?
What the critics say
"This action-packed new series tells the stand-alone stories of teens living in the fictional Mason Falls who solve various mysteries. In The House, Grace and a group of friends are determined to prove that a local house is not haunted, despite rumors that a ghost from the 1920s named Cordelia Rose haunts it. When a mysterious boy goes missing, Nick and Ava have a foreboding feeling and decide to help find him in Tracks. In The Turnaround, Justin decides to investigate the new baseball coach when the team begins to play suspiciously well and he suspects cheating. Hannah gets Behind the Screen when her older sister begins texting with a guy who does not seem to be who he says he is. Each story takes a realistic perspective and deals with real-life issues such as online scams and fighting with parents. VERDICT These books, written at a fourth grade reading level, are fast-paced with clear-cut resolutions to each case that will resonate with mystery and suspense fans." (School Library Journal)