A exploration submarine breaks the surface of the Arctic, breaking the ice as it goes up. Having done that, the team inside it exits the submarine, exploring the Arctic. They turn into a cave, and discover other teams in the past who have went to the Arctic but never returned, all frozen in blocks of ice. The team looks at the camera (presumably some unknown entity), gasps, and is frozen solid in the next second.
The cryogenic chamber keeping Mr. Freeze's wife Nora alive is damaged when the exploration submarine surfaced near it. It is determined that Nora will die without an organ transplant. Mr. Freeze returns with her to Gotham City, where he enlists the assistance of Dr. Belson, a former colleague now undergoing financial difficulties, who agrees to perform the operation if a suitable organ can be found. None are available that will suit Nora, who has a rare blood type, so Mr. Freeze resolves to kidnap a suitable "donor". After a search of the city's medical records, he sets his sights on Barbara Gordon - who is also, although Mr. Freeze of course does not know this, Batgirl. After Mr. Freeze kidnaps Barbara, he becomes the target of a police manhunt led by her father, Commissioner James Gordon, and a separate undercover search by Batman and Robin. Batman and Robin discover the location of Mr. Freeze's hideout - an abandoned oil platform - and set out to rescue Barbara. In the meantime, Barbara (who in the mean time proves herself to be a difficult prisoner who consistently manages to escape on her own). During the climactic fight, the oil rig goes up in flames; Batman, Robin, and Barbara begin to escape, taking Nora with them, along with an injured Freeze who vanquishes flames with his ice gun. As the group escapes, an explosion knocks Mr. Freeze off the rig, Batman being unable to save him even though he stayed behind. Freeze apparently dies as his glass helmet begins to shatter and he falls into the water. Batman, Barbara, Robin, and an unconscious Nora fly their way off the rig just in time as it explodes and sinks into the surrounding waters.
In the epilogue, a suitless Mr. Freeze, having cheated death via his pet polar bears, is seen wandering through the Arctic. He spots a log cabin, and peers through the window. Inside the cabin is a TV, which he overhears news of a resuscitated Nora Freeze who received treatment, courtesy of Wayne Industries. Mr. Freeze walks away in tears of happiness with his polar bears, and gradually disappears behind a blizzard.
- Kevin Conroy as Bruce Wayne / Batman
- Efrem Zimbalist, Jr. as Alfred Pennyworth
- Michael Ansara as Dr. Victor Fries / Mr. Freeze
- Bob Hastings as Commissioner Jim Gordon
- Robert Costanzo as Detective Harvey Bullock
- Loren Lester as Dick Grayson / Robin
- George Dzundza as Dr. Gregory Belson
- Mary Kay Bergman as Barbara Gordon / Batgirl
- Dean Jones as Dean Arbagast
- Liane Schirmer as Lieutenant Renee Montoya
- Jane Alan as Summer Gleeson
- Marilu Henner as Veronica Vreeland
- Rahi Azizi as Kunac
Batman & Mr. Freeze: SubZero has consistently received universal acclaim. With scores of 93% or higher being very common among top critics, it is the second highest critically rated movie in all of the Batman movies (the first highest being the successful movie, The Dark Knight, with a score of 95% and up).
Critics praised the redesigning of Mr. Freeze, especially his character history. Whereas in other forms of the Batman franchise Mr. Freeze killed in cold blood, in this movie Mr. Freeze was shown as a man desperate enough to do anything to save his wife. This redesigning of Mr. Freeze is also found in the episode Heart of Ice, in the original Batman: The Animated Series.
- Mr. Freeze
- Alfred Pennyworth
- Commissioner James Gordon
- Detective Harvey Bullock
- Lieutenant Renée Montoya
- Summer Gleeson
- Veronica Vreeland
- Dr. Gregory Belson
- Dean Arbagast
- Despite the film's home media covers claiming it not to have received an MPAA rating, the MPAA logo does appear in the film's end credits, indicating it may have received a rating from the MPAA, possibly PG for mild violence and thematic elements.