Bang! And then silence. No wreckage, no clouds, no conflagration in the neighborhood. Just a lingering mystery.

It's been the talk of the town for weeks now -- the boom.

Bill McDevitt may never find out what caused the terrific clap of noise that startled him from bed in the early morning hours about three weeks ago.

"It wasn't just a distant rumble. It sounded like lightning hit across the street. It was a sudden, loud, explosive bang," he said. "You get up and go look out the windows and you expect to see smoke or flames coming from the woods or somebody else's house, but I didn't."

McDevitt is just one of many north Pelham residents left wondering what's behind the blasts out of the blue. In the days following the first incidents, the town's online message board lit up with people swapping stories and cultivating theories.

Jill Atkinson, awoken by the same bang as McDevitt, thought her neighbor's home exploded. She expected to hear the approaching howl of sirens as she peered through her windows.

"I've never heard a house explode, but that's what I'd equate it to -- that level of noise," Atkinson said. "I was sound asleep and it woke me right up. I've heard transformers explode; this was more powerful."

Her husband slept on uninterrupted. He sleeps through anything, Atkinson said.

McDevitt and Atkinson haven't a clue as to what made the noise, but there is no shortage of theories in town.

Some say the source of the noise could be wooden boards cracking in the extreme cold of a New England winter, others the high-voltage power lines that cut through town. Other suspect a Tennessee Gas Pipeline compressor station.

Comment: how about a meteorite exploding in the upper atmosphere?

And straight out of the X-Files, there's defense contractor Raytheon's testing installation in town.

No one knows what goes on in there, McDevitt said.

In McDevitt's experience, the most comparable sound is a sonic boom, the shock wave that follows an object cracking the sound barrier.

It's difficult to calculate how many instances of the noise there have been. McDevitt heard it twice -- the initial incident and a second time in the afternoon two Saturdays back, he said.

"I'm not afraid of it. It just made a loud noise," McDevitt said. "I would hope it happens again and I hope to be outside and at least get an idea of where it came from."

Mention the bang to Fire Chief James Midgley and you'll hear a soft groan.

Residents aren't complaining, but he's fielded calls from the media and heard enough theories to make his head spin.

The chief doesn't have a theory of his own.

"I have no idea," he said with a chuckle. "I don't know, maybe it's aliens. Let's go with that for a while, let's see what kind of mileage we can get out of that."

The mystery boom has piqued Midgley's curiosity. He hopes someone gets to the truth of it, but he isn't holding his breath.

The noise hasn't injured anyone and there's been no reported damage, so it ranks low on the chief's list of priorities.

Unless somebody steps forward and admits they're behind the noise, McDevitt believes it will remain one of life's little mysteries -- an aural crop circle, a sonic Sasquatch, a listener's Loch Ness.

"All the investigating that anyone is willing to do has already been done," he said. "It could be a perfectly logical, rational explanation that has just escaped everyone."