The first sign of trouble was an unsettling rumble from beneath the streets, a trembling, grinding sensation that lasted several seconds.

Dan Stone felt it on the fifth floor of the cast-iron building he owns at 300 W. Pratt St. In a tavern downstairs, manager Christine Groller felt it, too, believing it was an earthquake.

It wasn't like that for Chad Cadden, but he was in a tunnel some 30 feet underground, the engineer of a thrumming diesel hauling 60 freight cars of paper, chemicals, wood pulp, soy oil, bricks and steel north to New Jersey.

Cadden felt the train lurch, then a light flashed on the instrument panel - the pneumatic control indicator - signaling that the emergency brakes were on. The train groaned to a halt in the darkness. Something had gone wrong.

It was 3:07 Wednesday afternoon, and an exhausting drama of fire, flood, worry and disruption had begun to unfold beneath the heart of Baltimore. At its south end, thousands of baseball fans sat unaware, watching the final innings of an Orioles loss. At its north end, more than a mile and a half away, the manager of a high-rise apartment building watched a plume of black smoke unfurl past the 11th floor, wondering if her longtime fears were about to be confirmed.

Soon, both ends of the tunnel would be cloaked by rolling black smoke. Because of it, the fire would yield its secrets stubbornly, and for an entire night there would be just enough mystery to trigger Civil Defense sirens and fears of a toxic disaster, while fire companies fought a two-front war against an enemy they could neither see nor understand.

But that wasn't all. A water main just above the tunnel would burst three hours after the derailment, gushing so much water that the level of Druid Hill Reservoir would drop 3 feet in four hours.

Only by sundown of the next day would the consequences seem clearer - a derailed tanker car leaking hydrochloric acid, several downtown buildings flooded by a torrent of 60 million gallons, enough broken telecommunications lines to disrupt e-mail around the world, two postponed Orioles baseball games (and another yesterday), and enough downtown gridlock to produce a year's worth of headaches and missed appointments.

Yet, for all the smoke and bother, not a single life would be lost, pending the unforeseen discovery of anyone who might have hopped aboard an empty boxcar. In this disaster, for once, every member of the cast would come out alive. But not without a few second thoughts about what might have been, had their luck turned for the worse.

3:07: The earth moves

It takes only a crew of two to run a freight train. The engineer mans the controls of the diesel engines while the conductor generally operates the brake, calls out passing signals and maintains the waybill, which carries the information of what's on board.

Cadden, 27, of Stewartstown, Pa., and conductor Edward Brown, 52, of West Baltimore, had just boarded the train a few minutes earlier, six miles short of the tunnel during a crew change at Curtis Bay. If there was trouble ahead, you wouldn't expect to encounter it in the tunnel, as straight a stretch of railway as you'll find on the CSX route through the city.

A signal just before the tunnel indicated the track ahead was clear, so the train continued. It was 3:04, and the train was lumbering along at just over 20 mph, black exhaust snorting from three engines at the front.

Looming to the left were the grandstands and warehouse of Camden Yards. The train entered the tunnel, its four headlights on, accelerating on a slight downgrade to about 23 mph before beginning the long, slow climb on the gradual rise beneath Howard Street.

That's when Stone and Groller were at work, in the building just above the tunnel at Howard and Pratt streets. And at 3:07, the earth moved.

"It seemed to be a grinding noise and a grinding sensation," Stone said. "I've been here for 11 years, and I've never felt anything like it."

"It lasted maybe 10 seconds," Groller said. "I honestly thought it was an earthquake."

Cadden and Brown weren't sure what to think, according to federal transportation officials who interviewed them. There was the lurch, then the flashing indicator, then the stopping of the train. Black fumes were everywhere, but that's often the case when three engines are running in a tunnel.

They tried to radio the CSX dispatcher, but no luck, probably because they were underground. Cadden used his cell phone, reaching the train master. It was 3:15. They were still unaware of the brewing disaster to their rear.