The killers seemed the wrong match to put in adjoining cells, a combustible combination promising no good. They were both callous, early adopters of a life of lawlessness. They could be wily. One had demonstrated escape skills. The other was a systematic schemer, reading blueprints, sketching maps, mulling over the fine details of crime.

Neither had much to lose.

They served their time on the so-called honor block, housing gained through good behavior that allows greater freedom of movement, the right to cook meals and the benefit of wearing street clothes in your cell.

The slick-talking neighbors, Richard W. Matt, 48, and David Sweat, 34, were serving lengthy sentences at the remote Clinton Correctional Facility in Dannemora, N.Y., a village in the Adirondacks near the Canadian border. It is a maximum-security prison where murderers and rapists are the norm, where extreme brutality is the common ticket in. Mr. Matt was serving 25 years to life, and Mr. Sweat life without parole.

Interviews with those who knew them from as early as when they were infants and those who put them away, as well as court documents, suggest little about them to admire. Both emerged from splintered families and curdled childhoods, the sort where you burn your own toys or run away on a stolen horse. They went on to compose bent lives, climbing their way up the ladder of crime to get to murder.