He appeared in the mission "Project Nova" commanded by Captain Viktor Reznov, where his team was ordered to find a Nazi doctor, Friedrich Steiner. Once they do, they enter a ship wreckage where they are betrayed by Dragovich after finding some Nova 6 gas, with Dimitri Petrenko, Vikharev, and Belov in one gas chamber, and Tvelin in the second chamber, along with Reznov and Nevski. While those in the first chamber were killed by the gas, Tvelin, Reznov, and Nevski escaped upon the arrival of British Commandos. However, while Reznov and Nevski escaped the wreckage, Tvelin is killed before he could do so.
The player is able to kill Tvelin without penalty.
He was not seen until he was thrown into the gas chamber.