Taking cover behind a clump of oleander bushes, two men peer intently toward the shadowy arches of the Colosseum across the street.
Plaid shirttails cover one man's gun. From his partner's leather jacket come binoculars to make sure they don't miss a move.Suddenly the binoculars go down and a yell comes from one of the watchers: "He took it. Let's go."
The "it" is a Minolta camera that Silke Ade, a 21-year-old nursing student from Germany, put down beside her as she spread out a map on a cool stump of marble column.
The taker is a suspected pickpocket and the watchers are a team from Rome's plainclothes anti-pickpocket police.
Dodging cars and buses, the officers dart across the street. Giuseppe Capurro handcuffs the suspect. Giuseppe "Pino" Agostinacchio presents Ade with her camera so fast she says she thought he was the thief.
The seasoned team makes the arrest look easy. But a day tailing Capurro and Agostinacchio around the hot city finds it's no Roman holiday tracking professional pickpockets who prey on distracted tourists.
Police get about 3,000 reports of theft by pickpockets each year - nearly 10 a day afflicting foreigners, Italian out-of-towners and Romans. They say thefts appear to have gone down since the special patrols began a few years ago.
Like the cops, the thieves are trained and work in teams.
Police break down pickpocket gangs by groups. Capt. Luciano Torchia, who directs the plainclothes squads, said Chileans and Peruvians, often sporting baseball caps, knapsacks and maps to look like tourists, tend to work mass transit. Algerians, who favor the businessman's look, stalk tourist sites.
The man arrested outside the Colosseum was a middle-age Algerian in a gray wool suit and impeccably pressed cotton shirt.
Bands of Gypsies prowl sidewalks and buses, often relying on smudged-faced, ragtag juveniles so they won't be prosecuted, Torchia said.
Italians don't seem to go in much for pickpocketing, concentrating on car thefts and apartment break-ins, police say. But tourists occasionally fall prey to young Italian thieves who zoom around on motor scooters, ripping handbags and cameras from people strolling on streets and squares.
While foreign pickpockets are usually ordered expelled after serving jail sentences, many slip back into Italy. Sentences are short: two or three months for a first offense, maybe a year for repeat offenders.
Capurro, 32, in brown corduroy slacks, and Agostinacchio, 30, in well-worn jeans, look like soccer fans going to a match instead of Carabinieri paramilitary police who usually wear red-striped black pants and jackets.
The pair like to get the lay of the land by strolling to Rome's main train station, a casbah of beggars and hustlers mingling with harried and sometimes confused travelers.
After a few years of working the beat, they have the faces memorized.
Capurro spots two women sitting on a curb near the bus depot outside the station. He says they are Peruvian pickpockets.
"On vacation?" Capurro asks cheerily.
"We're resting," one replies.
The officers haven't witnessed the women do anything, so can only let them know they've been spotted.
Bus lines that cross the heart of Rome are notorious for pickpockets. The No. 64, for example, is considered so risky a ride between the Vatican and the train station that some American residents have dubbed it "the heaven to hell" express.
Capurro and Agostinacchio ride the subway back and forth a few stops, but the only face they recognize is another undercover cop's.
They agree today's action must be above ground.
By now it's lunchtime, and tourists will be taking a break, maybe leaving cameras and bags perilously out of view.
On a grassy knoll near the Roman Forum, Japanese tourists sip sodas and take photographs. A bit apart, a man, his suit jacket draped over a shoulder, stretches out on the grass.
Capurro looks through the binoculars and exclaims: "There he is." Agostinacchio says they've arrested the man - the Algerian - before, for theft.
The Japanese throw away their soda cans but hang on to their cameras before getting back on the tour bus. The Algerian heads for the Colosseum and the two policemen follow.
They're sure their suspect hasn't spotted them, as the man, sweating in his wool suit, darts through and around the arches where ancient Romans once passed to take their seats for gladiator matches.
Capurro scurries behind a rack of snacks outside a van as the suspect saunters out. When their man seems to be eyeing Ade and a friend, the partners take up position behind the oleanders and watch the theft.
After the arrest, and a bouncy ride in a squad car through red lights to the station house, Ade gives details of the theft to another policeman who tells her she was lucky - she still has her camera.
His last report was a Danish couple whose suitcases were stolen as they checked into a hotel.