Aaron Green (Hill) gets things done. The ambitious 24-year-old has been given a career-making assignment. His mission: Fly to London and escort a rock god to L.A.'s world famous Greek Theatre for the first-stop on a huge comeback tour. His record mogul boss, Sergio Roma (Sean Combs), gives him one warning: "The artist is the worst person on Earth. Turn your back on him at your own peril." British rocker Aldous Snow (Brand) is a brilliant musician, but due to a bad break up and nose-diving career, has fallen off the wagon and is now a drunken disaster. Weary of "yes men" and scared he's entered the "greatest hits" moment in his career, Snow's in the midst of a nihilistic downward spiral. When he learns his true love, model/pop star Jackie Q (Rose Byrne), is in Los Angeles, Aldous makes it his quest to win her back... right before kick-starting his world domination. As the countdown to the concert begins, one innocent young man must navigate a minefield of London drug smuggles, New York City brawls and Vegas lap dances to deliver his charge safe and, sort of, sound... all while trying to remain faithful to his med student girlfriend (Elisabeth Moss). He may have to coax, lie to, enable and party with Aldous, but Aaron will get him to the Greek.