Up to her wrists in soapy water and dirty dishes, Agatha contemplates murder.

All the many poisons, arsenic, cyanide, curare, or the simpler, easier poisons from a household garden: pink rhododendron pollen in the honey, wild white hemlock in the pickle jar, delicate indigo wolfsbane. She rejects the too common, the too easily traced, but also the truly obscure, the impossible to prove. There must be a thread between the corpse and the killer, some tangible clew trailing through the labyrinth.

Guns, too: widely available, notionally controlled but easy to circumvent. Stolen from a friend, a lover, an enemy, the victim itself; borrowed from an acquaintance for self-protection; removed from the back seat of a cop car or the bathroom of a Baptist church. Bullets can be traced, so that’s fair; the gun itself can be found or hidden, thrown into a river, a lake, the sea, buried in some dumpster, tossed in a sewer or hidden under a pillow. The chrism of gunpowder on hands and chest, propellant and primer.

She figures the moment of opportunity, the tempting cliff edge, the convenient stairs, the car accident, the passing train. The unseen witness, the passerby with a memory for faces, the gas station attendant, the paperboy driving by at 3 in the morning, yawning deep in her chest, the flash of headlights on a shocked and bloodless face.