Let's face it, there's nothing quite like the feeling you get when a long wait turns out to be worth it. And Once writer-director John Carney is someone who really knows how to keep people hanging on. It's been seven years since that story of misfits and music piled on the surprise and delight like a sandwich from George's Street Arcade, making people fall for Dublin, or reminding them about the bits they actually loved about it in the first place.

Once was such a homespun and heartfelt film that you wondered quite how Carney could ever follow it up, and whether he could recreate any of its magic. Well, he did make a little-seen, shot-with-mates sci-fi spoof called Zonad in between, but to borrow an analogy that belongs in the worlds of Once and Begin Again, that was more a stop-gap EP. This is the follow-up album, and it proves that lightning can, pun intended, strike twice.

Carney's script again gives us two people who find each other at tough times in their lives and a love letter to a city that brings them together. Keira Knightley is Greta, a singer-songwriter who is adrift in New York after her humble troubadour boyfriend Dave (Maroon 5's Adam Levine making his film debut) goes down with a seemingly fatal case of what's known in the business as LSD - Lead Singer's Disease. Mark Ruffalo is Dan, the record company executive whose career has just gone the same belongings-in-a-box way as his marriage. While on a bender, he hears Greta play.

Don't worry about the familiarity of the plot, the bigger names or budget: there is just as much freewheeling charm, seat-of-pants energy and great songs - written by Glen Hansard and the New Radicals' Gregg Alexander, among others - in summertime New York as Carney found in Mountjoy Square and Killiney in colder weather.

Begin Again never gets too slick or too soppy and in Ruffalo and Knightley the pairing is unlikely but just right. He brings the same messiness and magnetism as his breakout in another gem, You Can Count on Me; she turns in one of her best performances and is a bit of a revelation on the mic. While Knightley says she doesn't want to sing again, she may have to have a rethink as Oscar night approaches.

It will do your heart good to watch and listen - let's just call this the feelgood hit of the summer.

Harry Guerin