Nate the Great and the Missing Key
Nate the Great doesn't especially want to go to a birthday party  for Annie's ferocious dog, Fang.  But he can't resist a mystery--and  when Annie loses her house key and can't get inside to set up the  party, Nate and his trusty dog, Sludge, are hot on the trial.  Their  only clue is a mysterious poem written by Annie's friend, Rosamond.   But nothing is too tough for Nate the Great--not even Fang!