Bowser is a mutt, just adopted by eleven-year-old Birdie Gaux and her grandmother, but when they all get home to Grammy's bait and tackle shop in the bayou they discover that their prize stuffed marlin has been stolen--so Bowser decides to investigate, and things quickly become complicated and dangerous.

"A bull shark in the swamp? No one in the Louisiana town of St. Roch believes it at first, but when a local boy has a face-to-face encounter with the toothy monster, every big fisherman is called out for the hunt. There's a big cash bounty on the shark. Sharp-eyed Birdie Gaux and her handsome dog Bowser can't help noticing that shark fever is causing some shady doings in town. For instance, where is Snoozy, the clerk who works at the Gaux family...

Dizzy the dog baffles his owner when he continues to disappear from the family's fenced-in yard, possibly flying around with his propeller-like tail.