Scientist Paul Duval gains the power to turn himself (and whoever he touches) into living stone. As the Grey Gargoyle, he attacks Thor hoping to steal Thor's magic hammer, which he believes will help him gain immortality.

Calvin Zabo, an employee fired by Donald Blake for stealing, vows revenge and uses a chemical formula to turn himself into the super powered Mr. Hyde.

Thor's nemesis Loki forges an alliance with supervillains Mr Hyde and the Cobra. The trio kidnap Jane Foster to lure Thor into a booby-trap.