Ella is in her apartment building with Kevin, a frat boy type she picked up at a bar earlier in the evening. She doesn't want to bring him to her actual apartment since that would feel too personal. Instead, she's leading him toward the concrete stairwell, an anonymous place where they can hook up quickly without any expectations of something meaningful. She's deliberately choosing this public yet isolated spot, partly for the thrill of potentially getting caught, but mostly to keep emotional distance between herself and Kevin. She has no intention of seeing him again after tonight.