Dr. Stephanie Lake is a minor character in Batman Beyond. Appearing in the episode "Meltdown", she was a genetic scientist working for Derek Powers who was tasked with curing Powers' genetic condition following his first confrontation with Batman. She was voiced by Linda Hamilton.
Dr. Lake had been hired by Wayne-Powers to research a cure for Derek Powers' radioactive mutation. She came up with a method of copying human neural patterns which could then be uploaded into a new cloned body, but required a test subject to practice on, someone whose DNA had been systemically damaged. She found the ideal candidate in Mr. Freeze, who had been rendered immortal due to the cryogenic chemicals that altered his body halting his ageing process.
Using Freeze's baseline DNA, Dr. Lake was able to create a clone body that did not suffer the same affliction that Freeze once had... or so it initially appeared. For a few days, Victor Fries enjoyed a new life as an ordinary human, but his new body soon began to show signs of reverting to his mutated state as he began to develop a deadly intolerance to even mild temperatures. Dr. Lake speculated that the cause for the reversion might have been a mnemonic agent in his DNA. Powers observed that the only way to be certain was to biopsy Freeze's organs at that stage in order to confirm this and find a way around the problem. Taking this as a suggestion, Dr. Lake locked Victor in a room and raised its temperature in an attempt to knock him unconscious. However, Freeze gathered enough strength to break his way out of the lab.
After escaping from Lake's lab, Freeze made his way to one of his old, abandoned storage facilities where he donned an advanced cryo-suit. With it, he returned to the Wayne-Powers compound with the intent of taking his revenge. He confronted Powers and Dr. Lake, freezing Powers in ice. He then turned his attention to the doctor and froze her too. Lake's death is not shown on-screen, but she screams as she is frozen and she never appears again afterwards, thus her death is confirmed.