After the 20 July 1944 assassination attempt against Hitler, Morell treated him with topical penicillin, which had only recently been introduced into testing by the U.S. Army. Where he acquired it is unknown, and Morell claimed complete ignorance of penicillin when he was interrogated by American intelligence officers after the war. When members of Hitler's inner circle were interviewed for the book "The Bunker," some claimed Morell owned a significant share in a company fraudulently marketing a product as penicillin.