Locke & Key: Breaking down what the keys are and what they do

Mending Key

The Mending Key has to be used on the Mending Cabinet to work—when inserted into the cabinet door, the key can mend anything placed inside the cabinet.

Nina Locke (Darby Stanchfield) uses the key to mend her cup, and experiments on books to see if the cabinet actually works.

However, the Mending Key does not work on people—when Nina tries to use the cabinet and the key on Rendell’s urn to bring her husband back, nothing happens.

Mirror Key

Another key created for the show, the Mirror Key allows the user access to a universe existing within mirrors. When inserted into a door or mirror, a reflection of the user appears, beckoning them into the mirror.

If one follows the reflection in, they find themselves surrounded by mirrors and reflections, which disorients them and makes it impossible to escape.

Nina almost becomes trapped inside a mirror before the Locke children devise a way to get her out—Tyler ties a rope to himself to help him lead Nina back to reality.

Music Box Key

The Music Box Key needs to be inserted into its accompanying music box to work—the person who inserts the key can control whoever they want and compel them to do their bidding.

In the comics, the Music Box Key would conjure a miniature version of the user in the music box to give out instructions. On the show, no such miniature appears, but the power of the key remains the same.