Angus Rickman (played by Roger Daltrey) is a marine colonel on an alternate Earth that was to be destroyed by a pulsar. The character was introduced in the episode "The Exodus". He had a fungus infection in his brain which required him to extract brain tissue from the brains of compatible "donors" and inject the tissue into his brain which causes him to temporarily morph into that person. Extracting brain tissue from these people caused them to go into a coma.
Three days before the pulsar was going to destroy his Earth, the sliders landed there, helped improve the sliding technology of local scientist Dr. Stephen Jensen, which allowed Rickman and 150 other people to slide to a safe alternate Earth before the pulsars hit. Rickman specifically had Wade Welles select 150 people that had brain tissue compatible with Rickman's to slide to the new world. Originally, the sliders were going to slide with Rickman and the 150 people, but Rickman ordered the slide early, and murdered Arturo when the sliders attempted to slide with him.
Rickman also murdered Dr. Stephen Jensen, the husband of Maggie Beckett, when Jensen learned that Rickman was responsible for the coma victims. Rickman lied to Maggie and said a mob had killed him.
Quinn, Wade, and Rembrandt slid to the Earth Rickman, Maggie, and the other 150 people slid (thanks to getting deep enough underground and the new ability to track wormholes given to them by Jensen), and informed Maggie there that Rickman murdered her husband. Initially, Quinn and Maggie wanted revenge on Rickman for murdering Professor Arturo and Dr. Jensen. However, Rickman still had the timer used to send him, Maggie, and the other people to this Earth. So Rickman used the timer to slide and escape from Quinn and Maggie. The timer Rickman was using also had the coordinates to Earth Prime, which gave Quinn, Wade, and Rembrandt greater incentive to catch Rickman. The sliders began chasing Rickman to parallel Earths so that Quinn, Rembrandt, and Wade can find their home coordinates, and so that Maggie could get revenge. Although initially both Quinn and Maggie wanted revenge, Quinn later decided against revenge and only wanted his home coordinates.
The first time the sliders encountered Rickman since "The Exodus" was in the episode "The Other Slide of Darkness". By this time, Rickman's face had changed from injecting the brain tissue of non-compatible donors and he was now played by another actor, Neil Dickson. In this episode, Rickman's timer broke, leaving him unable to slide. Rickman encountered Quinn's double, the first double of his that Quinn met, and Quinn's double was going to kill Rickman. Then Rickman told Quinn's double about Quinn and the others. Quinn's double then decided to give Rickman a deal: Quinn's double would not kill Rickman and would fix his timer, and in exchange Rickman would bring Quinn to his double. Rickman did this, so Quinn's double fixed his timer, and Rickman slid. After this, Rickman's timer was counting down like the Sliders timer, indicating that Quinn's double fixed it in the same way Quinn did the original timer.
The next time the sliders encountered Rickman was in the episode "Dinoslide". He returned to the world the survivors of his world slid to in order to harvest their brain tissue, but had to contend with dinosaurs and the sliders and was forced to slide when his timer ran out, but returned later. He was defeated again, but escaped once more.
The last episode with Rickman was "This Slide of Paradise". On this Earth, the sliders managed to take Rickman's timer away from him, leaving him stranded on this Earth. Quinn, Wade, and Rembrandt were about to use Rickman's timer to slide home and let Maggie use the other timer to continue sliding. However, right after they opened the vortex to Earth Prime, Rickman showed up. Quinn stayed behind to help Maggie fight Rickman but pushed Wade and Rembandt through the vortex. Rickman attempted to slide through the vortex to Earth Prime that Quinn pushed Wade and Rembrandt through, but the vortex closed just as he jumped towards it, and he fell off the cliff and died.
Read more about this topic: Recurring Characters Of Sliders