New Delhi, July 31 -- Only one stone wall remains of the old mother and baby home in this town, but it has cast a shadow over all of Ireland.

A mass grave that could hold up to nearly 800 infants and young children - some of it in a defunct septic tank - is being excavated on the grounds of the former home run by the Bon Secours Sisters, an order of nuns.

The burial site has forced Ireland and the Catholic Church - long central to its identity - to reckon with a legacy of having shunned unmarried mothers and separated them from their children left at the mercy of a cruel system.

The grave was accidentally discovered by two boys a half century ago. But the true horror of the place was not known until a local historian began digging into...