According to prosecutors, the woman got to know her attacker over Facebook. She was living in Paderborn at the time. He was living in Mönchengladbach, a town two and a half hours to the southwest, near the Dutch border.
She wanted to return home to Bulgaria. Also Bulgarian, the man reportedly offered to give her a ride.
But the trip turned into a living nightmare, according to the prosecution's statement, read at the start of the trial in Mönchengladbach.
The 34-year-old reportedly picked the woman up from her apartment in Paderborn in September 2016 and drove her to Mönchengladbach. Saying that they should stop for a coffee, he persuaded her to come into his house, according to prosecutors.
It was at this point that the series of horrific crimes allegedly started.
Once they were inside the apartment, he pulled her by the hair and began to rape her, the prosecutors said. When she tried to defend herself, he beat her unconscious. He then tied her to a chair and left her for two days and nights.
He then allegedly began to sell her for sex. She was instructed to always be nice to the clients - on average 17 of whom came every day, prosecutors report.
At the end of her day's work, he came and picked her up before once again forcing her to have sex with him.
“She no longer dared to resist him,” said prosecutor Alena Sellhorst.
On one occasion, while her captor wasn't present, the woman reportedly was able to call her brother who told her to run away. Her first attempt failed.
But in the second try, she was able to come by some money and rode in a taxi to Paderborn and then Dortmund. From there, she hoped to travel home with a bus ticket her grandmother had bought her.
But at Dortmund bus station she saw men who were associates of her captor and went in fear to the police.
As an interpreter translated the charge in court, the accused repeatedly grinned. His lawyer said that he denied the charges and that he would make a statement later in the trial.
The defence lawyer also said that his client had a question for his alleged victim: “Why had she done this to him?” he wanted to know.
But the case is complicated by the fact that the woman, who is the prosecution's lead witness, has told the court that she does not want to come to Germany to give a statement. The court is considering whether she can give her account via video link.
Judge Ralf Gerads made clear at the start of the trial on Wednesday how complicated proceedings would be without a lead witness. Other prostitutes who the woman named as witnesses have not yet been found.
Investigations will continue as the trial progresses.