Christmas Eve at The Nashville Rooms, a beery, boozy, affable crowd, everyone intent on getting drunk and having fun.
More hip revellers in the audience than rabid Elvis fans. I spent half an hour wondering why I wasn't at another gig down the road.
Suddenly there's a band on stage to shake all but the merriest out of Christmas contentment and seasonal good humour.
The Pop Group are hypnotic, different, frightening and irresistible.
The singer is a tall, painfully thin pillar of anguish, hands covering his eyes as he howls despair at the sedentary crowd.
Two diminutive guitarists prowl around his feet; the one with ginger hair and freckles croons catchy pop hooks as feedlines for the giant's desperation.
The other stares blankly into space until the climax of the set. Without warning he gyrates into a juddering, twitching solo.
The impact of The Pop Group is comparable to witnessing an epileptic fit or an unexpected fight. You want to turn away but the hideous fascination will not release your eyes.
Although we all climb obediently onto the tables and chairs to play mountain-goats for Costello, the drop in tension is noticeable and depressing.
Fortunately, Elvis and The Attractions play an imaginative and immaculate set, packed with new songs as exciting as the standards.
"Radio, Radio," for '70s cruising, and "The Beat" were outstanding, but by far the most unusual number was "(I Don't Want To Go To) Chelsea."
An extension of the "Watching The Detectives" pop-dub style, the theme builds and the melodies linger over insistent rhythms and curiously Latin-flavoured organ injections.
This isn't big news. No-one seriously doubted the man had more great songs coming and you'll hear them soon enough.
"Mystery Dance" closed the show but The Attractions trundled on Nick Lowe for a "Heart Of The City" encore.
Then a rocker, "Pumping Up" and time to go home.
It was a faultless exhibition of musicianship and material but an imperfect show because Elvis Costello gets a bit boring to look at after 15 minutes.
He does his itchy fingers, snarling spider routine and that's about it.
I enjoyed it because I enjoy his music, but it's the raw emotion of The Pop Group, the nightmare Monkees of tomorrow, that's still nagging my memory.