Mathieu Flamini scored in both halves to give Arsenal a 2-1 victory over arch-rivals Tottenham and a place in the Capital One Cup fourth round.
The Frenchman, making his first appearance of the season, smashed in on 26 minutes after Alex Oxlade-Chamberlain's fierce shot was parried straight to him by 'keeper Michel Vorm.
Chamberlain almost doubled the visitors' lead but Spurs equalised after the break when Nacer Chadli's cross-shot was turned into his own net by Calum Chambers.
Harry Kane had an offside goal disallowed and a scissor-kick effort cleared off the line but Flamini stroked home a sublime volley from the edge of the box to win the game late on - a trip to Sheffield Wednesday in round four the reward.
Both sides made extensive changes for the clash - eight for Tottenham and 10 for Arsenal - but Mauricio Pochettino may regret his decision to change both central defenders and play fifth-choice Federico Fazio.
After Joel Campbell, making his first start of the season, missed with a far post header, Fazio stood off Oxlade-Chamberlain on the edge of the box and then failed to react when Flamini mopped up the rebound to take the lead.
Spurs should perhaps have had a penalty when Danny Rose was clipped by David Ospina and was brought to the ground, having lifted a cross over the on-rushing Arsenal goalkeeper.
But they were fortunate to remain just a goal down at the break, Oxlade-Chamberlain steering a curling effort the wrong side of the far post after Fazio had gifted him the ball.
Tottenham upped the ante in the second half but Kane's goal, after Christian Eriksen's shot was tipped onto the post by Ospina, was rightfully chalked off for offside.
Andros Townsend also tested Ospina with a decent effort but the hosts needed Arsenal defender Chambers to give them a deserved equaliser, his outstretched leg turning the ball in ahead of Ospina.
Pochettino introduced both Heung-Min Son and Clinton Njie in pursuit of a winner in normal time and they came a hair's-breath away when Kieran Gibbs headed Kane's acrobatic effort, which had beaten Ospina, off the line.
But the team watched in horror when Fazio looped the ball high into the air into the path of Flamini, whose first-time volley found the bottom corner with 12 minutes left.