It seemed an innocent enough idea. After Barnaby Gilbert got laid off with a nice severance, his boss suggested he take up a new hobby to fill up his free time. On his regular commuter train, Barnaby got an idea what that hobby would be. He decided to satisfy a curiosity he’d long had. An avid birder, he began tracking some regular passengers — people he’d always wondered about — to see where they went and what they did. In this quirky, tongue-in-cheek thriller, he follows a Chinese man, a school girl and a sexy woman, using the same techniques he had to add hawks and herons to his life list. But he finds out pretty fast that humans were a much more dangerous species.