Continuity mistake: Mr Freeze's ship just appears out of the clear blue rather than having been anchored all night when you can play "In from the Cold."
Continuity mistake: Nora's cryo chamber changes in appearance in the three games it's in. 1. Arkham Origins DLC: Cold, Cold Heart. It looks like a big tube. 2. Arkham City Side Mission: Heart of Ice. It looks like a cabinet. 3. Arkham Knight DLC: In From the Cold. It's a tube again, like in Origins, but smaller.
Other mistake: If you have subtitles on while playing the DLC, In From The Cold, one militia member says the word "that" regarding Nora's cryo chamber. Yet the subtitle uses the word "the" instead.
Continuity mistake: In Batman: Arkham Origins DLC "Cold, Cold Heart," Nora Fries is wearing a long silver dress with her brown hair down at full length. Yet in the DLC "In From The Cold," she's wearing a short purple/dark blue dress with a bow around her waist, and her hair's now light brown and pinned back.
Answer: In Batman: Arkham City, Mr. Freeze's gun was taken by the Penguin, which he used in an attempt to stop Batman. After beating the Penguin and the eventual closing of Arkham City, the gun was then sent to the GCPD evidence room.
But Mr Freeze got it back for his fight with Batman, remember?
Rob245