The playwright's cleverly constructed work is set in two time periods, 1958 and the present day, and concerns the interrelationship of three characters: Philip (Hugh Dancy), Oliver (Ben Whishaw), and Sylvia (Andrea Riseborough). However, it's not a matter of seeing the characters age into their older selves. Rather, the individuals are the same age in each era, and yet the different social mores of their times have had a huge impact upon the way each has developed as a person.
In 1958, Philip is stuck in a job he doesn't like, married to Sylvia, and repressing his homosexuality, even as he embarks upon a brief affair with Oliver. In the present, Philip has just left Oliver because he can't deal with the latter's addiction to anonymous sex. Sylvia, who was trapped in an unhappy marriage in the earlier time period, is freer in the modern era, and is now friends with both men, particularly Oliver.
While there may be some initial confusion as the play starts flipping back and forth between the two eras, director Joe Mantello has made some very specific choices to smooth the transitions. Costume designer Mattie Ullrich has done a terrific job in making the clothing period-specific yet versatile, although David Zinn's set design -- a detailed interior in the first act, and an abstracted design in the second -- is not quite as effective.
The majority of kudos should go to the wonderful cast, who give detailed performances to differentiate the way they play their roles in each time period, while also showing enough similarities to make it clear that we are still seeing the same people (or at any rate, alternative versions of them). This is done partly through speech patterns, with the '50s-era individuals talking in more clipped tones than their modern-day counterparts. Also, the body language of each period differs, and the way the characters walk and gesture is specific to the age in which they live.
Dancy manages the difficult task of remaining sympathetic as his 1950s-self, even as Philip's words and actions towards Oliver and Sylvia can be quite cruel. Philip tries very hard not to let his emotions show, sometimes seeming maddeningly aloof. But his outward appearance belies both a fear and a strong passion, and a scene in which he goes to a psychiatrist (Adam James, in one of three roles, all played to perfection) is absolutely heartbreaking as you see the emotional toll that living a lie has had upon Philip.
Whishaw similarly navigates the trick of being extremely likable even when his modern-era character is clearly making some dubious choices, and engaging in behavior that is unlikely to win his boyfriend back. In both time periods, we're rooting for them because the two actors have a very strong and believable onstage chemistry, even though it's clear that Oliver and Philip are not necessarily the best match for one another.
Riseborough delivers an energetic and emotionally charged performance as a woman who both loves and is frustrated by these two men in her life. Sylvia's confrontation with Oliver in regards to his affair with her husband is especially well performed, and carries into her exasperation in the modern-era with Oliver's emotional neediness.
It's fascinating to see the way these three people have profoundly affected one another in both time periods. What's also interesting is that while Campbell paints a rather vivid and painful portrait of the way the sexually repressive atmosphere of the 1950s has damaged all of their lives, he also shows that the more permissive contemporary society has its own set of problems.