Felsen is a thin SPECTRE henchman who accompanies Irma Bunt and fellow guard Braun in their pursuit of Bond through the Swiss village near Piz Gloria. Tracking him to a shed filled with bells, both men brawl with the spy, but are overpowered by him. Although knocked out by Bond, the pair are woken up by Bunt in order to continue the pursuit.
Realizing that Bond has evaded them, the thugs return to their car and set off in pursuit, almost killing the spy as he attempts to use a phone-box to communicate with London. Sitting in the back of the car, Felsen tries to shoot at Bond's car on the highway, but is unable to get a clear shot.
In an attempt to evade them, Bond veers into the middle of a stock car race. As expected, Bunt and her men follow and carnage ensues. Sitting in the front passenger seat of the car, Braun manages to get a few potshots at Bond's car before his own car is toppled. The vehicle's occupants are forced to abandon the burning car before it explodes. Felsen is last seen Trying to help Bunt out of the vehicle.
Felsen final's fate is unknown. He is not among the victims in the final battle in Piz Gloria where most of Blofeld's soldiers lost their lives, but in all likelihood it is possible some of Blofeld's men from Piz Gloria may have been in the village near Piz Gloria at the time where not present maybe as a possibility Felsen is one of these, he may have more likely escaped with Irma Bunt possibly after the Mercedes-Benz W111 blew up at the stock car race where Bunt was caught in the blast it is likely Felsen may have looked after her when she was trying to recover from her scars.