Tottenham were embarrassingly dumped out of the Carabao Cup at Colchester after the Sky Bet League Two side won 4-3 on penalties.
After 90 goalless minutes, the U's took another Premier League scalp as Tom Lapslie hit the winning spot-kick after Christian Eriksen and Lucas Moura missed in the shootout.
It was a hugely worrying night for Spurs, which will do little to appease the notion that there are serious issues for Mauricio Pochettino's side this season.
Although Pochettino made 10 changes to his side, there was still enough quality on the pitch to be able to beat a side 71 places below them in the football pyramid, but they laboured badly.
They could not find the breakthrough and Colchester, who did not manage a shot on target in the 90 minutes, followed up their second-round win against Crystal Palace with an even bigger scalp on what is one of the most famous nights in their history.
There were debuts for 17-year-old Troy Parrott and 20-year-old Japhet Tanganga as Pochettino freshened up his side from Saturday's defeat at Leicester.
Despite the overhaul, which also included a first appearance of the season for Eric Dier, the visitors unsurprisingly assumed control of the match.
Parrott would have been dreaming of this night for some time and he almost made the perfect start but a low shot was deflected wide after he was played in by Dele Alli.
Alli, back in the side after his weekend rest, should have opened the scoring in the 18th minute after Spurs unlocked their hosts down the right, but the England international dragged his shot wide from Oliver Skipp's cross.
Spurs had almost all of the possession, but they were fairly pedestrian with the ball and it was only Moura who showed any intent or desire to break the lines.
A surging run saw him poleaxed by Spurs-supporting Colchester defender Luke Prosser and the Brazilian saw his free-kick parried by Dean Gerken, in what turned out to be the only shot on target in the first half.
Spurs were much better at the start of the second half and Parrott had another chance when he sent a near-post effort over the crossbar, before Kyle Walker-Peters struck a post with a cross-shot that beat Gerken.
Walker-Peters called Gerken into action with a swerving shot that was palmed away, but the wait for a breakthrough went on.
Eventually, Pochettino was forced to send on the cavalry in the shape of Eriksen and Son Heung-min in an attempt to get the job done, but it did not reap any rewards as Colchester held firm.
As they piled bodies forward, they suddenly became open at the other end and Courtney Senior saw his name in the headlines as he closed in on goal, but he put his shot just wide.
Spurs ran out of time and it went to spot-kicks, where they were beaten.
Eriksen saw the first kick saved by Gerken, but Spurs were handed a way back into the shootout when Jevani Brown's Panenka was saved by Paulo Gazzaniga.
Moura's effort then hit the crossbar, allowing Lapslie to rifle home the winning penalty to send the JobServe Community Stadium wild.
