Bagels on Board — Joan Betty Stuchner; Dave Whamond

All aboard! The Bernsteins are heading off on a cruise, and Aunt Sharon offers to take care of the family pets, Lox (the fish), Creamcheese (the cat) and Bagels, an energetic puppy with a talent for escaping. Trouble is, Bagels is up to his usual disappearing act. When he turns up unexpectedly on the cruise ship, Josh and his little sister, Becky, must keep Bagels hidden. But when an onboard mystery begins to unfold involving two potential spies and a mysterious woman with a secret envelope, Bagels just might be able to help crack the case!
   
Bagels on Board is the third book in the series about Bagels Bernstein, following Bagels Come Home and Bagels the Brave.