Jeff Hephner. Actor: Eric. Jeffrey Lane Hephner is an American actor, best known for the role of Jeff Clarke, first on the NBC television series Chicago Fire and then on its sister show, Chicago Med. More recently, he co-starred with Jennifer Garner in the action thriller film Peppermint. He also appears in the 2016 National Geographic TV series MARS and the Apple TV+ original science fiction space drama series For...