The metro car rocks gently, a rhythm that matches the stranger's fingers exploring the woman's ass. He pulls out a small bottle, drizzling lube onto his fingers, then onto her asshole. She tenses, then relaxes as he massages the tight pucker, preparing her for his thick cock. The train screeches to a halt, and they freeze, eyes locked, hearts pounding. The doors open, and a few passengers get off, breaking the spell. He unzips his pants, ready to claim his prize in the most public, taboo way.