Riverboat Roulette (Library Edition)

I do have an idea. The most important thing, though," I said to Margot, Mrs. Marvin, and Catherine, "is for you to act completely normal. Our big advantage is that the thief doesn't think that anyone will check the safe until we're already back in River Heights and he or she is off the boat. The culprit has no idea that we're looking for him or her."

Margot, Mrs. Marvin, and Catherine all nodded.
I turned to Buddy. "What time are we due back at the dock?"
"Ten thirty on the dot," he said.
I checked my watch. "Just under three hours," I said.
I'd never solved a case that fast before, but the dogs and cats of River Heights were counting on me!