Batman: Arkham City is full of really humanizing moments. From paying your respects to Mr. and Mrs. Wayne, to this one where you find Mr. Freeze's wife. This one little side quest goes a long way to show that Mr. Freeze is actually a dude beneath all of the armor and ice.
To get the 'Bargaining Chip' achievement, you've got to head over to where Joker's Playhouse is, and drop down to the bay. There's a boat in the bay, so make sure you land on that and not in the water. Once you're on the ship, throw a freeze blast into the water to make yourself a moving platform. Jump on the ice, grapple over to the wall, and explode it to gain entrance to where Mr. Freeze's wife is being held. There will be armed and armored henchmen for you to take down, so don't underestimate them.
- Xbox 360: 15G
- PlayStation 3: Bronze trophy