Zombie Army Trilogy - We Can Still Fix Him Achievement Guide
This during Episode 3 : Beyond Berlin : City of Ashes
After we save the guy above the hospital entrance continue on the path following the objective markers. I am not entirely sure if you need to save him, but that is what I have done - And to be honest I have played this level too much searching for the collectibles, I am pretty sick of this level now to go back through and look.
Continue on until you get to the radio, you will be over-looking the first area we were in. To the left of the radio is the man (Dr) we saved.
Interact with him, and then his bag, and run back to the room just after seeing the cribs with VI VI VI aboves them, the room where you encountered the Summoner.
On the bed below the words "You can still save him" interact with it, and after a little scene the achievement will unlock :)
Zombie Army Trilogy - We Can Still Fix Him Achievement Guide