While waiting on Androzani Minor for a couple days to meet up with Sharaz Jek to deliver weapons and gas carbines, he complained to Stotz about the wait. Stotz later scared Krelper by giving him a phony capsule that would kill Krelper but didn't.
Stotz and Krelper later decided to try and find Jek's hideout and steal his supply of spectrox. However, the Magma beast killed two of the runners. Krelper, Stotz and the only other surviving runner found Jek, who gave them two kilos of spectrox instead of eight. Stotz then decided to take the Fifth Doctor, who they thought was a government spy, back to their boss Morgus on Androzani Major for questioning. They tied the Doctor up on the bridge of the ship and left the bridge for a rest. However, the Doctor escaped and took control of the ship, landing it back on Androzani Minor. Krelper and the other surviving runner chased after the Doctor, but returned to the ship after a mud burst began.
Morgus and Stotz decided to raid Jek's headquarters and steal his spectrox supply, but Krelper and the other runner refused, as they didn't want to get killed by the mud bursts or shot by Jek's androids, and thought two kilos was enough. Stotz pretended to leave without killing them, but then turned around and shot and killed Krelper and the other runner. (TV: The Caves of Androzani)