Last month's story has disappeared into the big black hole of the www, so I've extracted a few pars from this one. (ps. the dancing ghosts refer to a story the twin's grandfather told about the cholera epidemic)

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"Duffy's Cut," as it's now called, is a short walk from a suburban cul-de-sac in Malvern, an affluent town off the fabled Main Line. Twin brothers Bill and Frank Watson believe 57 Irish immigrants met violent deaths there after a cholera epidemic struck in 1832.

They suspect foul play.

"This is a murder mystery from 178 years ago, and it's finally coming to the light of day," Frank Watson said

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In 2002, the brothers began digging and searching. They found forks and remnants of a shanty and, in 2005, what Bill Watson calls the "Holy Grail" -- a pipe with an Irish flag on it.

They knew they were close, but Bill said they knew they needed "hard science" to get them to the next step.

The science came from Tim Bechtel, a geophysicist, who learned about the project from a colleague at the University of Pennsylvania who had heard the Watson brothers speak. The friend knew Bechtel could provide the missing link in the brothers' excavation efforts.

Bechtel's work included earth scans, which can help detect what's underground without digging or drilling.

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...collected bones from seven skeletons unearthed at Duffy's Cut, including four skulls. The trays and containers of bones occupy a long, wide table in the back of a lecture room at the University of Pennsylvania Museum in Philadelphia.

Poring over the bones with her green spectacles sitting low on her nose, Monge said she has focused her attention on the skulls, adding that they have provided crucial clues to what might have killed the Irishmen at Duffy's Cut.

"This skull has a little divot on what would have been the side bone of the skull," she said, holding it up. "That little divot is something that didn't happen when they excavated it out of the ground."

With just one divot on one skull, she was reluctant to jump to conclusions. But as more skulls surfaced, a pattern started to form. Holding the second skull, Monge said with confidence: "This person was clunked on the head at around the time of death."

Two weeks ago, a new piece of evidence came up from the ground at Duffy's Cut: A skull with a perforation that could be a bullet hole. "In fact, we can see some nice cracked edges that do look very much like a bullet hole," Monge observed.

Monge and the team will soon test the skull for the presence of lead. The source could be a bullet or an ax. Either way, she said, "If they had cholera, it didn't kill them. I would say something else killed them, but they might have had cholera, too."

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