Algol II (also known as "Algol Two") was a planet, the second planet in the Algol star system. An M-class world, Algol was once the home to an advanced civilization. In the mid-23rd century, it was the site of Federation Starbase 45, built near the ruins of one of Algol's ancient glass cities.

One such city, Ithahulan, was over ten thousand years old, and the site of the mythical Well of Tomorrows, where the champions of Algol would go to divine their futures. Many glass spheres - identified as keepsakes - were excavated by archaeologists in and around the Ithahulan site. The ancient Provosts placed drops of water from the Well in these keepsakes, which would show the holder images of their future.

Following a battle with the Chakuun, the crew of the USS Enterprise took shore leave on Algol in 2255 while the ship was being repaired at Starbase 45. Lieutenants Mia Colt and José Tyler found a keepsake while visiting Ithahulan. Aboard the Enterprise, Colt subjected the keepsake to a tricorder scan which triggered the artifact and sent Colt into the year 2293, where her absence in the (relative) past had changed history. (EV comics: "Futures, Part One", "Future Tense, Part Two")

With the help of Christopher Pike, James T. Kirk, and the crews of the USS Enterprise-A, USS Excelsior, and the freighter Bounty, Colt was returned to Algol - which had been annexed by the Klingons in 2278 - where she jumped into the Well of Tomorrows and reappeared in her proper time mere moments after she left. Colt's report on the incident was classified, and a science vessel was dispatched to the Algol site. At the time, the keepsakes - including Colt's - no longer showed signs of temporal activity. (EV comics: "Futures, Part Three", "Now and Then")

It is possible that this planet is in the same star system as Algol Prime, or is the same planet.
planets visited by the USS Enterprise (NCC-1701) (2243-2264)
Robert April's command (2243-2251) EarthRomulan planetoidTarsus IVFaramondAlpha Tau IVUsilde
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