It's the early 1960s in Los Angeles and George Falconer (COLIN FIRTH) is an English professor whose lover of sixteen years, Jim (MATTHEW GOODE), has now been dead for eight months following a fatal single car accident. George has continued existing but not really living, leaning on his friend and one-time heterosexual lover, Charlotte (JULIANNE MOORE), for support, while observing the domestic life of neighbor Susan Strunk (GINNIFER GOODWIN) and her family.
He's also continued teaching, although his material has become more philosophical, drawing the attention of one of his students, Kenny (NICHOLAS HOULT), who seems interested in his professor for more than just academics. George, however, has no intention of doing anything with that as he's planning on making this day his last, his continued grief and emptiness driving him to that decision.
Yet, rather than do anything spontaneously, he meticulously plots his suicide, tying up loose ends and putting his estate in order. As the day marches on toward his fateful decision, George contemplates his past and present while interacting with Charlotte and, to his surprise, Kenny who may just give him enough hope to reconsider what he has planned.