The lords of the city of Waterdeep hire a team of adventurers to investigate an evil coming from beneath the city. The adventurers enter the city's sewer, but the entrance gets blocked by a collapse caused by Xanathar, the eponymous beholder. The team descends further beneath the city, going through Dwarf and Drow clans, to Xanathar's lair, where the final confrontation takes place. Once the eponymous beholder is killed, the player would be treated to a all blue window describing that the beholder was killed and that the adventurers returned to the suce where they were treated as heroes. Nothing else was mentioned in the ending and there were no accompanying graphics. This was changed in the later released Amiga version, which featured an animated ending.