German Denis hit a hat-trick to complete a stunning Atalanta comeback, beating Internazionale 4-3 at the San Siro.
In a two-thirds empty stadium, Tommaso Rocchi scored his first goal in 14 months on the stroke of half-time to put the hosts ahead.
Giacomo Bonaventura levelled on 56 minutes following a good assist from Inter-owner striker Marko Livaja and an error by Walter Samuel, but Inter regained the lead only 61 seconds later as Ricky Alvarez pounced on a loose ball to make it 2-1.
And Alvarez made it two goals in five minutes with a wonderful solo effort, which at that point seemed to secure a comfortable three points for the former European champions.
But Denis halved the deficit on 65 minutes from the penalty spot before stunning those few home fans who did turn up, netting in the 71st and 77th minutes to put the visitors ahead for the first time and complete a memorable treble.
Making matters worse for Inter, Antonio Cassano pulled up with an injury to his right thigh, while Atalanta finished the game with 10 men due to a stoppage-time red card for Cristian Raimondi as he scuffled with former team-mate Ezequiel Schelotto, who only left the club in January.