Artist Chitta Dey will always remember the day a 55-year-old inmate of Calcutta's Alipore Central Correctional Home showed him a bunch of landscapes by him. In every painting the sky was missing. When Dey asked him the reason, the man, who had already served 15-plus years of the life sentence given to him, replied: "Sir, I don't have any sky. I've lost it forever."

This was in 2007. Egged on by B.D. Sharma, the then inspector-general of correctional services - West Bengal, Dey had just started holding art workshops for the inmates. It was part of the "cultural therapy" project Sharma had initiated in prisons across the state.

The prisoners - some of them notorious convicts - had shown a keen interest in the visual arts. From what Dey says, the empty canvas was at once their tabula rasa and also the receptacle for the outpourings of the wild imaginations of these tethered lives.

"We held a number of exhibitions with their paintings. Many were critically acclaimed and some even found buyers," says Dey, who organised workshops to familiarise them with the basic skills. Today, the Alipore Correctional Home houses many of these artworks and sculptures in its Sristikala Bhaban. The initiative itself resonated in other neighbouring geographies.

Dey won accolades, life went on, but those words about losing one's sky forever continued to haunt him.

In between, Dey continued to chase his olden dream of an in situ rock-cut sculpture of a flock of birds. The graduate from Calcutta's Government College of Art & Craft wanted to revive India's long lost art form of rock carving on the lines of Elephanta, Mahabalipuram and Ajanta-Ellora. And he planned his gargantuan project far away from the city, in Purulia.

Things started to fall in place. The then chief minister, Buddhadeb Bhattacharjee, offered him a 800-foot hill in the Matha Pahar range in Purulia's Baghmundi village. He got a grant of Rs 2 lakh from the state government. He had around 40 students from among the local tribals, most of whom were Santhals. They were first taught how to handle the chisel, hammer and drilling machine, and then rock-climbing, rappelling, erecting scaffolds to etch gargantuan birds with wing spans ranging from 55 feet to 120 feet. The plan was to etch at least 100 birds in a way that all of them would be visible from the foothills.

But it was not all smooth sailing. Interruption came in various forms. There was the perennial fund crunch and then, at one point, the sculptors were rounded up by the police who suspected them of being Maoists. The Pakhi Pahad or bird hill project was almost abandoned.

And then in 2008, the wheels began to turn. Pranab Mukherjee, who was then a Union minister, took personal interest in the project and arranged for a grant from the erstwhile Planning Commission. Armed with sufficient funds, Dey now decided to revive the project and also infuse it with a new life. "I planned to involve prison inmates who would be able to work under the open sky. I wanted to give them back a portion of the sky they'd lost."

In March 2015, the Alipore Home finally agreed to "loan" Dey six inmates for a couple of days for a pilot project at Pakhi Pahad. "This year we took 10 inmates to our campus," says Dey. These prison artistes keep at it during the cool months - October to March - as the hills are extremely hot the rest of the year. Those months, carving sessions stretch between 8.30am and 3pm. The inmates are paid a daily wage for their creative work.

Along with sculptures of birds on the hill, the team is working on 30 boulders in the area. They will be carving out some near-extinct local animals such as pangolins, spotted deer and other local birds. "This is for posterity. Even if the animals become extinct these rocks will tell their story."

Surajit Basu is one of the sculptors at work. A former railway employee from Dinajpur, he was convicted for murdering his brother-in-law and handed a lifer of which he has already served nine years. He says, "When Pakhi Pahad is ready, people will know I am one of the creators."

And though some of them may well be behind bars, perhaps borne on the wings of appreciation, they will always live close to the sky.