Caldriss was one of the Brotherhood's deadliest assassins before his retirement from active duty. His calculating nature and an eye for details have found him a job where his attention to details profited him - an auditor and collector of dues for the Brotherhood. Interestingly, he is one of the Brotherhood members who actually met the Vault Dweller.
He was sent to the town of Cold Water to collect three stolen power armors and the bodies of the thieves, after the Warrior finished his mission here. At the time, he didn't think much of it though. Later in the game he can be found in Bunker Epsilon.