Karl is a double amputee, but not by accident, birth or disease. He is an amputee by choice.
Six years ago, Karl (who asked that his real name not be used) sat alone in a parked car with 100 pounds of dry ice and an obsession to destroy his legs.
"The first thing I did was I used a wooden flour scoop to scoop some granulated dry ice into the bucket. ... It filled the wastebasket with carbon dioxide gas, which was 79 degrees below zero," he said.
Over the next 45 minutes, Karl put his legs in the wastebasket and then kept adding dry ice until it got to the top. "I spent the next six hours well-packed in the dry ice, and then I'd add more dry ice to keep it topped off," he said.
A chemistry major in college, Karl had done his research well.
"I'd done all the thermodynamic calculations, the mass of tissue, how much heat you had to subtract from that tissue to achieve freezing temperatures," he said. "And I knew that after six hours I had certainly achieved more than enough to freeze the full thickness."
After those six hours, Karl calmly drove himself to an emergency room, using the automatic hand controls he had installed in the car.
Within days, his legs began to blacken as the frozen tissue died away, and within a month surgeons had no choice but to amputate both of Karl's legs.
Karl is not a one-of-a-kind medical mystery, however. There are others like him, who believe their bodies don't match the picture of themselves they have in their minds.
"I wasn't born in the correct body," said Lilly, who has twice tried to amputate her legs. "The mind doesn't connect up to the body at all."
Dr. Michael First, a psychiatrist at Columbia University in New York, is one of the few researchers to study patients with this strange obsession to lose one or more of their limbs. The rare condition is called body integrity identity disorder, or BIID.
"When these people see an amputee, they see ... a person of strength being able to overcome hardship, someone to be admired," First said.
Aside from this obsession, First said his BIID patients can appear to be mentally healthy.
"The most striking thing about these people, is that if you were to meet one, you wouldn't have a clue that there was anything unusual about them," he said.
The fascination with being handicapped nearly always begins in childhood, said First. Karl said the first inkling that he wanted to be an amputee came when he was just 5 or 6 years old.
He often took refuge from his own family life in the home of a neighbor who was disabled by polio. Then he saw a young amputee.
"It was kind of like the proverbial light bulb going over the cartoon character's head," Karl said.
His first reaction, he said, was envy. But still, Karl said he considers himself normal.
Dan (who asked that his last name not be used) is a biomedical engineer who lives and works in a small town near the French Alps, and he has carried the same obsession as Karl's throughout his life.
Dan, who is intensely physical and loves hiking and skiing, said he had thought of amputating his own leg using dry ice and a power saw. To reduce his anxiety, he sometimes pretends to be an amputee.
Even when he is exercising, Dan said, "I find myself imagining, OK, how hard would it be, wearing a prosthesis?"
Dan said that if he does decide to amputate his leg, he would consider it a "rational" act. "Having my leg off would cause a handicap and suffering," he said. "But BIID also causes handicap and suffering, and it's just a matter of which is worse."
Most doctors consider the act of removing a perfectly healthy leg or arm to be unethical. Unfortunately, that doesn't stop the obsession. In fact, Dan's obsession got so bad last year that he searched and located a surgeon in the Philippines who would perform an amputation for a price -- one leg for $10,000.
In the end, Dan said the steep price and questions about the surgeon's competence kept him from following through.
Lilly, however, was determined to finish the job. She mutilated her left leg last year by freezing it with dry ice, hoping doctors would be forced to amputate it.
"I have no more ankle. My foot is swollen all the time," she said.
So far, doctors have not complied with her wishes.
Lilly (who also asked that her real name not be used), like Karl and Dan, said her obsession began in childhood. "I used to play that I was an amputee," she said. "In that little world I was normal. I felt complete. ... I felt good."
Lilly also knew exactly where she would want each of her legs to end -- with the right leg two centimeters longer than the left.
For years, Lilly kept her strange wish locked deep inside her, even after she married and started a family in a little French town on the Mediterranean Sea.
But her husband, George, said there were signs that things were not quite right. "She used to do things that didn't make sense," he said. "She used to bandage up her legs, especially at night when she was alone."
Lilly said when she told her personal physician in France about her obsession, he said that if she went through with it, he would have her committed to a mental institution. Eventually, Lilly confessed to George.
George was understandably shocked, but he ended up standing by his wife. And Lilly began looking for a surgeon who would help.
In the late 1990s, a British surgeon named Robert Smith amputated the legs of two physically healthy patients at a hospital in Scotland, sparking a furor in the British press.
Smith said he performed the surgery to end his patients' obsessions and suffering. "They may take the law into their own hands," Smith said. "They may lie under a railroad line, on a railroad line and get run over by a train. They use shotguns and shoot their limbs off. They really are a desperate bunch."
And Lilly was indeed desperate. When she learned about Smith, she and George traveled to the hospital in Scotland where he worked. She froze her legs in dry ice near the hospital.
But Lilly could not stand the intense pain long enough. By the time she entered the hospital, her legs were badly damaged but there would be no amputation.
The ordeal has left her crippled but unbowed in her quest for an amputation, and Lilly said she has no explanation as to why.
Her husband, George, continues to help her. "It is difficult because it's not a normal thing to do," he said. "It is her body and she's gonna do it. I'd rather be there and make sure that no one gets more hurt, and that she doesn't lose her life doing it."
Today Lilly, Dan and Karl all chat on the Internet occasionally, though Karl's story has taken a sobering turn.
Karl said his obsession with losing a limb did not end with his double amputation. But he said he finally lost his desire to also remove his left hand after an intense regime of therapy and anti-depressants.
For a man remarkably at home in his wheelchair, there is a hint of regret. There are places the wheelchair can't take him, like to the beach to feel the sand under his feet.
"It's all those little things, like that," Karl said. "What the hell was I thinking?"