The metro's hum vibrates through them as they stand, pressed together, anonymous in the crowd. Her breath hitches as his hand finds her thigh, tracing upwards, pushing her panties aside to reveal her slick heat. He grunts, his cock hardening against her ass as she reaches back, guiding him inside her. The train lurches, their bodies slamming together, their silent coupling punctuated by the screech of metal on metal, the dim lights casting their entwined shadows on the grimy floor.