Who Let You Go by The Killers delves into themes of longing, regret, and the complexity of romantic relationships. The song features a narrative where the protagonist struggles with the departure of a significant other, questioning who allowed them to leave and reflecting on the pain of lost love. Key themes include heartbreak, introspection, and the emotional turbulence that comes with realizing someone has moved on. Poignant moments in the song include the chorus, where the repetition of the question 'Who let you go?' highlights the protagonist’s desperate search for answers and closure.