Evidence
- First, we've seen how the hitman operates. It is hardly a stretch to imagine him taking out Adam in the process of killing Camilla. In fact, I think it's a bit of a stretch to imagine him killing only Camilla. This guy murdered a vacuum cleaner salesman. Check out the scene where Linney James, the casting director, takes Betty to meet Adam. Linney tells Betty, "Now we want to take you across and introduce you to a director who's a head above the rest. He's got a project you will kill." Notice she omits the word "for." Then Linney says excitedly, "Knock right out of the park." …Right out of the Park Hotel — the hotel where Adam is staying.
- The blue box represents the truth of Diane's actions — the truth she has locked away and tried to forget. With that in mind, consider the scene showing Rita lying on Aunt Ruth's bed. She is in the same foetal pose that we later see the corpse lying in, and Betty is checking her temperature (is she dead?). In the background we see an open blue box — Betty's suitcase — sitting on the bed.
- Back at the airport: Betty leaves with the old couple carrying not one but two blue suitcases. After the old couple depart, Betty turns and exclaims, "My bags?" when she sees her suitcases have gone. Betty could have said "My luggage?" or "My suitcases?", but she says "bags" — the only word that could refer to both the old couple and the two blue cases.
- Betty's relationship with the old couple is an almost perfect repetition of Diane's relationship with Camilla and Adam. First we see Betty and Irene arm in arm riding down an escalator — the old man is nowhere to be seen. Outside the airport he appears and takes Irene away. A few minutes later we see the couple driving off with sinister grins, suggesting their kindness was never sincere. Compare this to Diane's experience on Mulholland Drive: Camilla takes Diane by the hand and leads her up the hill; at the top, Adam appears and takes Camilla away. Later, Camilla and Adam whisper and laugh as they make their announcement, apparently enjoying themselves at Diane's expense. Perhaps Camilla's love for Diane was never sincere either. Notice also the similarity between Adam's glasses and the old man's glasses.
- At the end of the film, the monster behind Winkie's sets down a paper bag. Inside: the blue box, some raw meat (death), and a beverage-can tab (something has been opened). Then the old couple crawl out of the bag. They are on their way to Diane's apartment to seek vengeance — because she had them murdered. They are Adam and Camilla.