Dilmer III was the inhabited third planet in its star system. It was home to the Dilmerians, a pre-industrial humanoid civilization. The planet's core created a spacetime differential that resulted in time dilation, such as that for every second that passed in the rest of the universe, a week elapsed on the surface.
In 2382, a quantum fissure opened near Dilmer III, and a purple USS Enterprise-D from an alternate reality passed through "while battling some evil clones of Tasha Yar, or something." The Enterprise returned to its own dimension, but Lieutenant Commander Data was left behind, resulting in a shuttle crash on the planet that destroyed Data's body.
After a Starfleet observation buoy picked up the new rift, the USS Cerritos was sent to Dilmer III to seal it. However, the ship detected Data's signal on the planet and sent an away team consisting of Lieutenant junior grades Beckett Mariner, D'Vana Tendi, and T'Lyn to recover Data so as not to risk the local's discovering him, thus interfering with their technological development. Disguised as Dilmerians, the three Starfleet officers recovered the android's head and destroyed the shuttle wreckage, but became stranded on the planet for a year of relative time due to a transporter mishap. During this time, T'Lyn opened a thriving produce and haircare business while Mariner got into legal trouble and Tendi sought to find a way off of the planet with the help of Data. Despite some troubles, the three managed to preserve the Prime Directive and were eventually beamed back to the Cerritos with Data's head.
Afterwards, the Cerritos launched Data into the rift in a torpedo casing to be recovered by the purple Enterprise before the Cerritos sealed the rift. (LD: "Fully Dilated")