People come to Allahabad to wash away their sins in the sacred River Ganges. For many it's the realization of their life's goal, and they emerge feeling joyful and rejuvenated. But there is also a darker side to the world's largest religious gathering, as some take advantage of the swirling crowds to abandon elderly relatives.

"They wait for this Maha Kumbh because many people are there so nobody will know," said one human rights activist who has helped people in this predicament and who wished to remain anonymous. "Old people have become useless, they don't want to look after them, so they leave them and go."

Anshu Malviya, an Allahabad-based social worker, confirmed that both men and women have been abandoned during the religious event, though it has happened more often to elderly widows. Numbers are hard to come by, since many people genuinely become separated from their groups in the crowd, and those who have been abandoned may not admit it. But Malviya estimates that dozens of people are deliberately abandoned during a Maha Kumbh Mela, at a very rough guess.

To a foreigner, it seems puzzling that these people are not capable of finding their own way home. Malviya smiles. "If you were Indian," he said, "you wouldn't be puzzled. Often they have never left their homes. They are not educated, they don't work. A lot of the time they don't even know which district their village is in."

Once the crowd disperses and the volunteer-run lost-and-found camps that provide temporary respite have packed away their tents, the abandoned elderly may have the option of entering a government-run shelter. Conditions are notoriously bad in these homes, however, and many prefer to remain on the streets, begging. Some gravitate to other holy cities such as Varanasi orVrindavan where, if they're lucky, they are taken in by temples or charity-funded shelters.