Songfacts®:

• Smith wrote this song with Jimmy Napes (Naughty Boy's "La La La," Disclosure's "Latch"). He told 4Music in a track-by-track: "I wanted to make a Norah Jones-esque record with a heavier beat. This is the same chord pattern again and again. It's complex in its simplicity."
• The song is a track from In the Lonely Hour, an album that tackles Smith's lack of a love life. "On 'Latch' I was singing about love," Smith told The Guardian, "but I've never physically experienced it. And I'm kind of sick of listening to albums about the turmoils of relationships, never having had one. So I wanted to write an album for people who have never been in love. I want to be a voice for lonely people."
• The song's music video was directed by Luke Monaghan, who also worked on Smith's "Leave Your Lover" clip. The visual was filmed in LA and picks up on the song's theme of infidelity as we see Glee's Dianna Agron portray the scorned wife of the cheating Chris Messina (The Mindy Project).
• The song tells a heartbreaking story that Smith observed first hand. "It's about a marriage that I've been an observer of," he explained to Digital Spy. "I put myself into the woman's shoes."
  
  "The person I wrote it with, we both knew them and we just vibed off each other," Smith added. "We both had really strong opinions on what the woman was doing. It's quite a complex song. When you listen to it you think it's just bashing a guy for cheating, but it's not, it actually talks more about how the woman's a mug. She knows she's not the only one, but she's never going to leave. I think that's wrong."
• A$AP Rocky spits some rhymes on Smith's remix of the song. We hear the New York rapper tap into the song's theme of infidelity as he becomes that cheating lover. He names the girl that he wrongs Sasha Fierce, which is also the moniker that Beyoncé gave her sexpot alter ego.
  
  So Sasha Fierce
  A whole lot of tears
  Rolling down her cheeks
  Crying 'til she's sound a sleep
  Preach, pray that today is not a lonely one.
  
  It was BBC Radio 1 DJ Zane Lowe who suggested to Smith that he should do a remix with a rapper. "For me this sounded more like a jazzy track, but Zane Lowe was actually the one who said - he rang me up and left a voice mail on my phone - and was like, 'Sam, this is a hip-hop track. You need a rapper on it'" Smith told Digital Spy. "So he kind of inspired us to get a rapper on it and just show a different life to the music. I've always said my music is genre-less, and I always want it to remain that way."