This continues in Detective #604, where the story of Clayface IV is revealed.
Based on the story from Detective Comics (DC, 1937 series) #40. Origin of Basil Karlo, the original Clayface.
The origin of Matt Hagen, the second Clayface, adapted from Detective Comics (DC, 1937 series) #298 with a humorous twist.
The story of Preston Payne, the third Clayface.