Police said the model was sent by her agent in the United Kingdom to Milan for a photo shoot on July 10 and kidnapped by a man who posed as a photographer the following day.
"Attacked, drugged, handcuffed and closed inside a suitcase, that's how a 20-year-old English model was kidnapped on July 11 in Milan to be sold to the best offer on pornography sites", said a statement from Milan police.
But when she reached the studio the next day she was assaulted and drugged, then placed in a auto boot and taken to a small village near Turin where she was kept prisoner by Lukasz Pawel Herba, a British resident born in Poland, police said.
A Polish man, who lives in Britain, was arrested on July 18 on suspicion of kidnap and extortion, state police said.
Her kidnapper reportedly demanded €300,000 off her agent in the United Kingdom to prevent her "sale" online.
No one took part in the online auction, so it was unclear if Herba had the necessary contacts to organise such an operation of was something of a fantasist, according to the police.
In a letter sent to the victim upon her release, Black Death told her that a "mistake" had been made in capturing her.
It has been reported that the captor demanded £50,000 upon the woman's release and threatened to kill her if she told police about the incident.
Authorities said the kidnappers were going to release her "because she had a 2-year-old child" and their "rules exclude kidnapping mothers".
Upon arriving at the apartment, she was attacked by two men, according to local police.
It is understood the police investigation involved reconstructing the kidnapping scene and studying CCTV footage from the area.
On July 17, for reasons that are not clear, Herba drove the woman back to Milan and released her close to the British Consulate, where he was arrested.