Journey into Mystery / Thor Vol 1 #458

Plot

With the true Thor residing in Asgard and engaged to Sif, Eric returns to earth as Thor to continue his heroic exploits; Eric encounters Shatterfist and is plagued by the thought that now he can be killed (he met the villain in the future circa Thor #440 and learned that he would not die until after he met his foe in the present); Eric goes to the Avengers for advice; He meets Sif at the Mansion and she professes her love for him but he does not know that she is really the Enchantress in disguise; Amora sends Eric to Asgard to "rescue" the real Sif from Thor; Thor and Eric battle and Sif is injured in the conflict which makes Thor very, very angry.