Nate the Great and the Big Sniff by Marjorie Weinman Sharmat

Nate the Great and the Big Sniff : Paperback : Random House USA Inc : 9780440415022 : 0440415020 : 11 Feb 2003 : Nate depends on his dog, Sludge, to help him solve all of his cases. But Sludge can't help him this time because he's lost inside a big department store on a rainy day. Nate looks high and low, but every clue leads to a dead end--until Nate realizes that Sludge "can" help him. Illustrations.