Captain Idris Janek was the Captain of the USCSS Prometheus. He was a part of the ship' misson to an alien planet. He died after he flew the Prometheus into the Engineer's ship to stop it delivering the black liquid to Earth.
Janek is uninterested in what the domes contain, but he does care about the safety of the people on board. After finding out what the bacteria inside the urns can do, he tells Shaw to make sure nothing is brought back to Earth, while he agrees to Shaw's suggestion that if she fails he also shall do anything on his part to do so. Once Shaw warns the Prometheus that the Engineer has started his ship and has set course for Earth to kill all humans, Janek sacrifices himself by crashing Prometheus into the alien ship, successfully stopping it. His co-pilots decide to stay on board with him even after he tells them to go to the escape pods, demonstrating their loyalty as they go down together.
Janek seemed to enjoy playing his accordion and singing old Steve Stills songs. He may have also slept with Vickers after he asked her if she was a robot.