You cannot open this without Part 1, Part 2, and so on.
With the Enhanced Edition available on modern platforms, why do people still hunt for these original RAR parts? game-planescape.torment-(10597).part3.rar
If you’ve stumbled upon this specific naming convention, you’re looking at a relic of the "split-archive" era. Back when bandwidth was limited and file hosts had strict size caps, large games (Torment originally shipped on four CDs!) were broken into smaller .rar chunks. You cannot open this without Part 1, Part 2, and so on
If you are currently staring at part3.rar on your hard drive: Back when bandwidth was limited and file hosts
Are you trying to get this specific version of Planescape running on a modern PC, or
This specific filename, , is a fragment of a multi-part compressed archive typically found on file-sharing sites or older digital repositories.