By Sanjoy Majumder
BBC News, Delhi
"When I woke up, I felt this terrible pain on my abdomen. They told me they had taken out my kidney.
Mr Ahmed is the only earning member of his family
"I thought I was going to die."
Shakeel Ahmed only wanted to come to Delhi to find work.
So when two men approached him outside the railway station offering him a construction job, he readily agreed.
"They drove me to a house far away. On the way they asked me some strange questions like if I had any diseases," he says.
Later that night he was transferred along with two other men to another house.
"There were these men in green coats they took a sample of my blood.
"I was given an injection and I passed out."
Shakeel and two other victims are now being kept in a solitary ward in a civic hospital in Gurgaon, an affluent suburb of Delhi, under the watchful eyes of a policeman.
They were brought here by the police, who found them during a raid on an illegal clinic.
It was the first hint that they had stumbled on a massive racket involving millions of dollars and reaching out to all corners of India and even some countries abroad.
"Many men, mostly poor labourers, were brought here and their kidneys removed," says Gurgaon police commissioner Mohinder Lal.
"They were offered between $1-2000. The recipients were wealthy clients in India and other countries. Some of them were from Greece, Arab countries, United States and one or two patients from European countries."
An international investigation is now under way. Interpol has been alerted to look out for two doctors believed to be the kingpins of the operation.
But in India a debate is now beginning on why so few people come forward to donate their organs.
An estimated 150,000 Indians need a kidney transplant every year, but only 3,500 are available.
One of the needy is Kamal Verma.
A year ago he was told that he would need a transplant or undergo dialysis for his failing kidneys.
"The laws in India are so that it makes it impossible to get a kidney legally.
"I can only get one from a blood relative."
It's one of the major reasons for the thriving black market.
"Every hospital has a tout. In fact, the doctors or nephrologists will often suggest a person that you can contact to get a kidney. They charge up to $10,000.
"But I don't have the money and in any case it's illegal so I don't want to go down that route."
So the once active trade exhibitor is now resigned to a life of virtual retirement.
"I can barely see, I can't do a strenuous job, I get short of breath. My life is finished," he says as he suns himself on the terrace of his modest flat.
It's this hopeless mismatch between demand and supply that is being ruthlessly exploited by some doctors and agents.
Mr Ahmed's parents look after him in the hospital
And fuelling it is a million-dollar black economy that has spread its tentacles across the country.
Especially in small town India.
Meerut is a little over an hour's drive east of Delhi.
Its central market is busy, its narrow, congested lanes choked with people, vehicles of all shapes and sizes and stray animals.
On one side is the decaying red brick town hall.
Sitting on the steps or squatting on their haunches outside are daily wage labourers.
They wait for business, pulling on bidis (country cigarettes) while some play cards. Others nap.
Many of them have already sold their kidneys.
"I needed the money," says Om Prakash simply.
A house painter, he's in his forties but looks a decade older.
His cheeks are hollowed, his eyes glazed and his skin is stretched tight over his bones.
'Who can refuse?'
"Three years ago some men said they'd pay me 80,000 rupees ($2,000) for my kidney.
"Who can refuse? People kill for money this isn't that bad."
There are many like him who need the money to buy food and support large families.
Back in the Gurgaon hospital, Shakeel Ahmed's aged parents look at their exhausted son.
"He was the only one earning in the family," says his father
"I have another son who's unemployed and a daughter who's divorced with five children.
"What'll we do for money?" he says, wiping his eyes.