The heart-shaped pendant was worn by Tally while she was in The Smoke. It was given to her by Dr. Cable, the leader of the Specials. Tally was supposed to open it when she arrives at the Smoke and send a signal using an eyescan. It would then send a signal to Doctor Cable, informing her of the location of the Smoke. Shay thought it was from an old crush back in New Pretty Town.
Tally tried to destroy it in a futile attempt to save the Smoke and continue her romance with David. However, it was designed to send a signal to Dr. Cable if it was damaged. Cable came a few hours later. Her Specials arrested the Smokies and destroyed the Smoke. This led to Tally and Shay's first fight. Shay had to be dragged away screaming after trying to harm Tally.