The blood trail from the mother-daughter murder in Jagacha has led to a sordid tale of sex, blackmail and vengeance.

The cause of the killing is saved in the mobile of victim Srabonti Ghosh, who had allegedly captured on her camera phone prime suspects Samir Barik and Somasree Das in compromising positions.

“The duo confessed that they killed Srabonti, 27, first and later eliminated her daughter as they did not want to leave any witness,” said Niraj Singh, the superintendent of police (Howrah).

Howrah police on Wednesday said Somasree, 29, was involved in an extra-marital relationship with Samir, 35. For the past three months the two used to meet in her neighbour Srabonti’s house.

For the past few weeks, Srabonti — who, too, apparently had an affair with Samir — was blackmailing Somasree and him with photographs she had captured on her camera phone.

While the two women are neighbours in a Jagacha colony, Samir lives in Duttapukur, North 24-Parganas, with his wife and son. Somasree has a six-year-old daughter and is now pregnant.

Samir and Somasree were desperate to ensure that the photographs were not leaked and their affair was not exposed.

So, on February 26, the two confronted Srabonti and when she refused to hand over the cellphone containing the damning photographs, they killed her and then her eight-year-old daughter Prapti.

“Somasree and Samir used to frequent Srabonti’s house in the absence of her husband Partho. Samir apparently paid Srabonti Rs 500 every time he came to her house with Somasree,” said police superintendent Singh.

“But then Srabonti started demanding more money. She even started blackmailing them with the photographs she had in her possession,” he added.

In the afternoon of February 26, Srabonti was watching TV in her bedroom while daughter Prapti was sleeping. Somasree reached neighbour Srabonti’s house in Asutosh Ghosh Lane, of Jagacha, around 2.30pm. Samir arrived minutes later.

During interrogation on Tuesday night, Samir broke down and confessed that they had first asked Srabonti to hand over her mobile phone, but she refused.

A heated altercation broke out, with Srabonti threatening to raise an alarm and alert Somasree’s in-laws, who live within shouting distance, about her extra-marital affair.

“Samir donned a pair of surgical gloves and tried to silence Srabonti by throttling her. As she slumped to the ground, he first strangled her with some cloth and then stabbed her with a sharp weapon,” said an investigating officer who had heard out Samir’s confession.

“Suddenly, little Prapti woke up and the two panicked. Somasree then slipped on another pair of surgical gloves, smothered the girl with a pillow and then stabbed her once,” he added.

After the double murder, the two took Srabonti’s mobile phone and left. Somasree went home while Samir threw the blood-stained gloves next to a pond and took a rickshaw to reach Kona Expressway. From there, he boarded a bus and returned home.

A probe revealed that Samir had visited Srabonti’s house alone “nine to ten times over the past two months”. Her husband Partho, a BPO employee, was in the dark, police said.

“Interrogation is on to trace the mobile phone, the only thing missing from the Ghosh house,” said an officer, adding that the call details of Somasree’s cellphone had led to Samir’s arrest from his Duttapukur house on Tuesday.