Zimmer, 58, is a very serious, very straight-forward scientist who has traveled to Rivet City from the Commonwealth (Massachusetts) and is in town on business for "the Institute." Zimmer is looking for an escaped robot, an experiment that, in ZImmer's words, is "unstable, and a danger to himself and others." He is, without exception, always in the company of his bodyguard, Armitage.
After picking up the trail once he got to the Capital Wasteland, Zimmer eventually made his way to Rivet City in the hopes that fellow scientist Dr. Madison Li could assist him in his search for his missing android. On arrival to the Rivet City science lab, he was refused the right to speak with Li by Anna Holt, Li's assistant. Despite being refused assistance, he remains within the lab, refusing to leave and demanding to speak directly with Li. He will refuse to leave until Li, "Stops playing with her chemistry set and starts talking real science." It should be noted that Dr. Zimmer shows utter contempt and disgust for Rivet City and its residents.