Dust speckles shelves up on the third story. Wood floors creak. Walls and cabinets in the cramped office, tucked into a red-brick Baltimore rowhouse, channel a generation’s worth of sloganeering.

“We shall overcome Reagan”

“Nuclear Free Zone”

“Don’t buy war toys”

Lawrence Egbert comes here almost every weekday, taking calls on an old white push-button phone with a handset darkened by years of smudged newsprint and perspiration. He climbs the stairs, slower now since a bicycle accident two years ago cracked his pelvis, but steady and resolute.

Amid the kaleidoscope of distractions, a lumpy white garbage bag slumps on the floor against a metal bookshelf. Egbert doesn’t object when I ask to peek inside.

I pull the yellow drawstrings, and the bag sags open. A muddle of plastic lies before me. Long plastic tubes twine around each other, refusing to let go, like stubborn tendrils of ivy clasping tree branches.

Egbert, a slightly built, genial and energetic retired anesthesiologist with a snowy goatee, turns to his computer, his back to me, content to answer an e-mail while I sort through the pile. Once I finish untangling, I hold in my hands a curious plastic sack, about 21 inches long and 18 inches wide. A bunched white elastic strip, reminiscent of a garter, circles the mouth at the open end. A thick plastic tube runs into the sack, stretching 37 inches before branching into a T-shape with 12-inch arms extending from each side of the joint.

Egbert calls it an “exit hood.” It’s a contraption that can end a life in minutes. The 84-year-old doctor, who formerly served as a campus Unitarian Universalist minister and has taught as an assistant visiting professor at Johns Hopkins University, offers to explain how it works. The tube connects to two helium tanks, he says. He lifts the hood over his head and lowers the open end, letting go as the garter clamps to his forehead. Then, he says, you release the valves on the tanks, str...