He then started work on the idea that became "Citizen Kane". Knowing the script would take time to prepare, Welles suggested to RKO that while that was being done—"so the year wouldn't be lost"—he make a humorous political thriller. Welles proposed "The Smiler with a Knife", from a novel by Cecil Day-Lewis. When that project stalled in December 1939, Welles began brainstorming other story ideas with screenwriter Herman J. Mankiewicz, who had been writing Mercury radio scripts. "Arguing, inventing, discarding, these two powerful, headstrong, dazzlingly articulate personalities thrashed toward "Kane"", wrote biographer Richard Meryman.