Superstore Surprise - Grand Format

WHO IS GERONIMO STILTON ? That's me ! I run a newspaper, but my true passion is writing ADVENTURE stories. Here in New Mouse City, the capital of Mouse Island, my books are all bestsellers ! My stories are funnY , fa-mouse-ly funny. They are whisker-licking-good tales, and THAT'S A PROMISE ! SUPERSTORE SURPRISE : My cousin Trap was opening a superstore ! I had been excited for the grand opening but, holey cheese, it was a disaster ! The lights wouldn't go on, the speakers were broken, and something was stinking up the place.
Someone was trying to sabotage the store. But who could it be... and why ?