Possible Clues:

• Whom Jekyll becomes
• ___ Park, New York birthplace of F.D.R
• 39 Down's evildoer
• ___ Park Corner (London tube station)
• Titular villain of 1886
• Timothy denied concealing evil alter ego
• Title alter ego of 1886
• Literary alter ego in cloak, say
• Homicidal alter ego of fiction
• Jekyll’s alter ego