Possible Clues:

• *Literary character with an evil alter ego
• Stevenson character with a sinister alter ego
• Change joint and faulty key left with large bookish character working in medical profession, on and off
• Two-faced medic has something to hide reportedly?
• Counterpart of a noted alter ego
• Victorian GP subject to mood swings
• Evil Robert Louis Stevenson character
• Silver article on broken pipe in sacred spring
• Medic, otherwise a part of 25