Ashbury, Witney, and London, 2012-2013
Rachel rides the train from Ashbury to London and back again every day because she's pretending she still has a job (fun game). She passes through her old town, Witney, which is where she spies on Megan, Scott, Tom, and Anna. These are real-world locations but they're not very important. Aside from gin in a tin, the book doesn't feel particularly British; it could be set on any public transit line.
What Passes Beneath
However, there is one thematically significant sub-setting: the Underpass. It sounds creepy, doesn't it? Underpass. It's a simple tunnel under the tracks, but the whole "under" part makes it eerie, like passing through hell.
It's even more hellish because this is where Rachel has her big blackout and where Megan goes missing. We get our first look at the underpass through Megan: "That smell of cold and damp always sends a little shiver down my spine, it's like turning over a rock to see what's underneath: moss and worms and earth" (2.48). Ah, sounds homey, doesn't it?
Absolutely not. Every image of the underpass is creepy, from its "blackened tunnel mouth" (7.22) to the comparison to a "black hole last Saturday night" (11.8). It's a physical structure that stands in for fear. Rachel eventually has to face her fear of what she forgot that night and return to the underpass to learn what really happened. Shudder.