|Introduced In||Live Together, Die Alone|
|Owned By||Kelvin Inman|
|Found By||Desmond Hume|
The fail-safe key was first mentioned by Kelvin when he and Desmond were underneath the Swan Station at the system termination spot. Kelvin explains that "the incident" was electromagnetism and geologically unique. He goes on to add that there was a leak, so now the charge builds up, and every time they push the button, it discharges it before it gets too big. Desmond ponders why they are made to push the button if they can just turn a key to end it. To which Kelvin chuckles, adding an analogy of how it would be like pulling your finger out of a dam and letting it all blow instead.
When Desmond finally left the station and followed Kelvin deep through the jungle eventually to a cove where Kelvin was fixing up his sailboat, the two engage in a physical altercation, and Kelvin appears to have been killed. Desmond grabs the key from around his neck and runs back to the Swan.
Desmond hides the key inside his copy of "Our Mutual Friend" which he kept inside the Swan's bookcase. After the computer was destroyed by Locke, Desmond retrieves the key and uses it on the system termination. The turning of the key activates a high-field discharge around the island, and implodes the hatch, expelling Desmond, Locke and Eko outward. (Live Together, Die Alone)