Arret was an inhabited planet. This was the homeworld for the Arret natives, a warp-capable humanoid species. The planet was located in the same position as Earth in the Milky Way Galaxy in the positive matter universe, but in the reverse negative antimatter universe.
Karla Five and her son Karl Four lived on this planet during the mid-23rd century. The inhabitants of the planet began their life at an old age and slowly grew younger. Brain functions, language and operational controls worked in reverse of what they did in the positive matter universe, as the flow of time was reversed.