In the fictional Star Trek universe, Walter Keel was a Starfleet Captain commanding USS Horatio. He had also been a close friend of Jean-Luc Picard, and Jack Crusher. Captain Keel died uncovering a conspiracy against the Federation in which small aliens would enter host bodies and take control of them.

By 2365, Captain Keel had become suspicious of certain strange behaviors exhibited by some at Starfleet Command. He was able to find other officers who had similar concerns. Eventually, Keel contacted Captain Picard and asked for a meeting on a deserted planet. Keel and the other officers told him of their suspicions regarding Starfleet. What none of the others suspected was that Captain Tryla Scott - one of the officers in league with Keel - had already been compromised. Picard was not totally convinced, but was willing to keep his mind open for the time.

After the meeting, the Enterprise encountered the wreckage of the Horatio. Captain Keel had been killed. While Starfleet authorities made an initial finding of negligence against Captain Keel, as these authorities were themselves compromised, this would not be true. What actually happened was that some members of the Horatio crew had been compromised, and they carried out sabotage that destroyed the ship.