Wednesday's rush-hour bomb attacks against civilians in Mumbai could have the unwanted effect of derailing the latest timid steps towards reconciliation between India and Pakistan.
This is not a foregone conclusion. But avoiding further bloodshed can be achieved only if past grievances are put aside in favour of well chosen words, and careful diplomacy.
So far the signs are promising. Pakistan has expressed shock, and India has been cautious not to assign blame. We hope level heads continue to prevail.
India, of course, is no stranger to terrorism wrought by Pakistan's hands. Killings in the same city in 2008 - claiming 160 lives over a 60-hour siege - were eventually tied back to the Pakistani creation of Lashkar-i-Taiba. It might be natural, then, to assume that the first instinct would be to look towards Islamabad.
Instead the opposite has happened. Indian Mujahideen, an offshoot of the banned Students' Islamic Movement of India, is receiving most of the early speculation. Other domestic organisations, from Kashmiri separatist groups to various criminal networks, are equally capable.
It would be asking too much of human nature to expect the Indian people and their government to be entirely serene about this strike. Sudden slaughter is intolerable anytime, and even worse when repeated. But the best the region can hope for is that India's leaders continue to proceed deliberately and cautiously.
For a government under fire domestically - the prime minister reshuffled his cabinet on Tuesday amid a raft of corruption allegations - this will prove no easy task. Pointing fingers is always easier than owning up to failures within. But falling into the too-familiar blame game ultimately serves only the bombers, who are obviously eager to fish in waters roiled by bitterness and blood.
Taking their bait could have devastating consequences.
Just three weeks ago Pakistan's foreign secretary, Salman Bashir, had two days of Kashmir talks in Islamabad with his Indian counterpart, Nirupama Rao. While nothing concrete emerged this was indeed a positive step for two nuclear-armed rivals.
It would be a shame if the bombs of terrorists in Mumbai were allowed to dictate the terms of this relationship.