India has seen the cycle repeated 13 times in nearly three years: Bombs are planted where they can kill as many people as possible. Investigations follow, memories fade and months later, bombs explode in another city.
But with 552 people dead since October 2005, security forces remain chronically undermanned and ill-equipped, and the political elite appears unwilling to take the sweeping action experts say is needed to stop the bloodshed.
"What has been done between the last attack and the latest atrocity to augment our ability to stop terrorists, to root them out? Nothing," said Ajai Sahni, a former chief of India's domestic Intelligence Bureau.
He called India's police forces and its intelligence agencies "hideous and hidebound" and noted that in a country where hundreds of millions of people worry every day about finding enough food to eat, "every politician knows that security issues don't win or lose elections."
On Saturday, 22 explosions tore through the centuries-old city of Ahmadabad, killing at least 42 people a day after seven smaller bombs left two dead in the technology hub of Bangalore.
By Tuesday, police had traced an e-mail taking responsibility for the Ahmadabad blasts and two cars used in the attack to a suburb of Mumbai, India's commercial center, and had detained at least 30 people for questioning and arrested one possible suspect.
Authorities also defused 18 bombs found Tuesday near the main diamond markets in the city of Surat, 175 miles south of Ahmadabad, and issued a sketch of a young man believed to be linked to one of two explosives-filled cars discovered there.
'These terrorists are never caught'
But just as in the past dozen attacks, there was little expectation the police would come up with anything more than a few small timers, if that.
"These terrorists are never caught. The politicians are only talking. The police only know how to take people's money," said Ashok Patel, echoing commonly heard sentiments in India where police are often seen as shakedown artists.
The 45-year-old shop owner works down the street from where one of the bombs left bodies sprawled around carts piled high with mangos, pomegranates, bananas and oranges.
The choice of a market crowded with shoppers was clearly planned. The bombers have repeatedly hit targets that draw the biggest crowds: a temple during evening devotions in the Hindu holy city of Varanasi, commuter trains during rush hour in Mumbai, a mosque just as Friday prayers were ending in the southern city of Hyderabad.
The latest spate of bombings is not the first time predominantly Hindu India, born alongside Muslim Pakistan in the bloody partition of the subcontinent at independence from Britain in 1947, has had to contend with Islamic militancy.
In 1993, bombings in Mumbai left 257 dead. A 2001 attack on India's Parliament killed 14.
But in those attacks, and many other earlier ones, the culprits and their motives soon became clear. Mumbai was bombed in revenge for the demolition of a historic mosque by Hindu extremists. The Parliament assault was the work of militants fighting to end Indian rule in predominantly Muslim Kashmir, the Himalayan region at the center of the India-Pakistan rivalry.
In both attacks, the assailants were believed to have been aided by compatriots in Pakistan.
'Unable to crack any major terror cells'
While officials also see a foreign hand in the latest attacks, they remain uncertain as to groups involved or their exact aims.
"We have to accept that it is fellow citizens who are carrying out these attacks. They may get help from Pakistan, but they are Indians," said Sahni, the former Intelligence Bureau chief.
Beyond that, officials remain puzzled.
"We have been unable to crack any major terror cells and this is limiting what we know," said an official with the Home Ministry — which oversees domestic security — who spoke on condition of anonymity because the sensitivity of the matter.
The names most frequently mentioned are Pakistan-based Lashkar-e-Tayyaba, Bangladesh-based Harkat-e-Jehad-e Islami or the banned Students' Islamic Movement of India.
E-mail suggests Muslim recruits
The last group is of most concern to authorities. It is believed to be behind an e-mail that claimed responsibility for the Ahmadabad attack for the obscure Indian Mujahideen, and it is entirely home grown.
The e-mail's subject line said "Await 5 minutes for the revenge of Gujarat," an apparent reference to 2002 riots in the western state that left 1,000 people, most of them Muslims, dead. Ahmadabad was the scene of much of that violence.
The e-mail certainly suggests extremists are finding recruits among India's Muslims, who make up about 14 percent of the country's 1.1 billion people and lag far behind the Hindu majority in almost every social indicator, from household income to literacy.
Nonetheless, the latest e-mail does not explain what prompted the previous dozen attacks or who was behind them.
Answering those questions, experts say, would take a major revamp and expansion of India's security forces.
India has just 126 officers per 100,000 people compared to the United Nations norm of 222, and many police spend "most of their time guarding VIPs or working traffic stops" — a prime source of bribes, said Sanker Sen, a security analyst and retired policeman.
Few have the training or tools to do anything but the most rudimentary investigations.
In India, "it's called modernization when we give shoes to a barefoot policeman," Sahni said.
India's elite law enforcement agencies have more capable officers — but far too few. The Intelligence Bureau, for example, has only 3,500 field agents handling everything from counterterrorism to financial crime.
Making matters worse are politicians who appoint loyalists to top police posts and look to the forces as a source of patronage and a tool for going after rivals, Sahni said.
Ordinary Indians, meanwhile, are putting little pressure on the country's leaders to stop politicking and tackle the problem.
"We've had linguistic riots, wars with Pakistan, caste conflict, religious riots," said historian Ramachandra Guha. "We are a society that is used to living with danger and minor catastrophes and stumbling on."