2007: at the end of a momentous day, Charlie, Stella and John cross paths under the arches of Paddington Station. As Charlie locks eyes with Stella across the platform, a brief, powerful spark of recognition flashes between them. But they are strangers ...aren't they? Plunging back thirty years we watch as, unknown to them all, the lives of Stella and John, and Charlie and his girlfriend Beth, are pulled ever closer, an invisible thread connecting them across the decades and through London's busy streets. For Stella, becoming a young mother in the 1970s puts an end to her bright academic career in a way John can't seem to understand. Meanwhile Charlie gambles all future happiness with Beth when his inner demons threaten to defeat him.