A 31-year-old woman was allegedly molested by an acquaintance inside his car late on Saturday night and then thrown out onto EM Bypass, police said on Sunday.

A mother travelling in another car with her family responded to the cry for help from inside the car at 11.50pm and got off to help the victim, a bank employee.

But Nilanjana Chatterjee, the woman who had stopped to help, was left with a fractured leg and gash in the head when the assailant’s Honda City hit her during his hasty bid to flee.

The bank employee, allegedly molested in the car near the Ruby intersection, had a swelling in the head from a wound and face injuries.

Nilanjana was returning home with husband Deep Satpati and their daughter from her mother's birthday dinner at the Abhyudoy Housing Complex off EM Bypass at Anandapur.

When the couple heard a woman scream for help from a car behind them on an otherwise deserted stretch, Satpati pulled over. “I realised that as a mother, I had to help someone who is not much older than my daughter,” Nilanjana, who is in hospital, told The Telegraph later.

Satpati had positioned his Maruti Alto in a way that the Honda City would be forced to slow down. “Probably realising he was trapped, the man opened the front door and pushed the woman out,” a police officer said.

“The road was deserted," Satpati recalled. “Nilanjana got off and walked to the left side of the Honda City, where the woman had been thrown out. As the Honda City made a U-turn to escape, one of its front wheels passed over Nilanjana’s left leg and the car’s nose hit her head, leaving her with a deep cut.”

Satpati added: “Everything happened so fast that I couldn’t note down the car’s number.”

Officers said the victim had told the police she had recently met the accused, who had introduced himself as Amitabha Bose, and had gone out for a drive in his car on Saturday night.

Investigators have detained a man in connection with the case.

The police have learnt that the woman hails from north Bengal and lives in rented lodgings in the city.

Nilanjana Chatterjee and her husband Deep Satpati, who responded to the cry for help from the bank employee File picture

They said she had told the police that trouble began when she asked to be dropped home. “According to the woman’s statement, she could sense danger when the man refused to take her home right away. As the vehicle was passing in front of the Abhyudoy Housing Complex, the woman again sternly asked him to drop her home,” an officer at Anandapaur police station said.

The man then allegedly molested her and hit her, prompting her to cry out for help.

Nilanjana said the victim was shivering in fear as she held her tightly. “I tried consoling her even after the car ran over one of my legs.”

With both women crying in pain, Satpati dialled 100 to alert the police. Officers from Anandapur police station arrived quickly, while a traffic sergeant arranged for an ambulance.

Sources said footage from the spot purportedly shows a Honda City passing a housing complex in one direction and, about a minute later, passing it again from the opposite direction at high speed.

An official at the Ruby General Hospital said doctors had recommended that the woman undergo a CT scan and an X-ray but she refused and was allowed to leave in the presence of the police.

He said Nilanjana had suffered fractures in her left tibia and fibula and would need surgery.