Jordon Ibe's first Premier League goal for Bournemouth condemned Arsenal to a 2-1 loss on the south coast, with Alexis Sanchez conspicuous by his absence.
Ibe's first strike for the Cherries in 46 league appearances sunk the Gunners, who leaked two goals in five minutes in this turnaround defeat.
Callum Wilson's third goal in four league games had Bournemouth level after Hector Bellerin handed the visitors a lead they could only squander.
The defeat, and its manner, proved another blow to Arsene Wenger, with the Arsenal boss now resigned to losing key attacker Sanchez in the January transfer window.