Batman (1940 Series) Annual #11 (1987)

By Alan Moore & George Freeman and Max Allan Collins & Norm Breyfogle. 

“Mortal Clay”  

Preston Payne, "Clayface," falls in love with a store mannequin named "Helena" who he believes is a real person.

He takes up residence in the department store that houses her, hiding all day and coming out only at night to be alone with her.

Although they begin very much in love, their relationship takes a turn for the worse when Clayface begins to suspect she is committing infidelities.