The opened Music Box.
The Music box, owned by the Hysterical Dame, is the opposite side of the Storefront window portal.
The Music Box key.
This portal was originally blocked due to HD having misplaced the key. Slightly later in the adventure, she found it
around the neck of her Teddy Bear. She promptly uses the key, finding Problem Sleuth looking through the Storefront window portal. She soon closed the box after seeing Mobster Kingpin looking through her window. This action resulted in Problem Sleuth being killed by a monster.
The Music box was used for the second and last time when Ace Dick used the Storefront Portal to avoid falling to his death, which consequentially shrunk him due to the size-warping capabilities of window portals. The Music Box was then sliced in half by HD accidentally, never to be used again.