Northampton Town suffered late heartbreak at the Abbey Stadium as Cambridge scored a late winner.
David Amoo struck a crucial winner in the 94th minute of the contest to decide the fixture.
The visitors had taken the lead through Aaron Pierre and re-took the lead via a Junior Morias strike after Jevani Brown had equalised.
But Cambridge equalised through George Taft and the game had looked to be hurtling towards a draw until Amoo’s late intervention saw the home side win it.
The result sees Northampton sit 6 points above the drop-zone after Macclesfield beat Oldham.
Northampton took the lead through Pierre just before the half-hour. The visitors had already hit the bar when Pierre struck the ball into the back of the goal.
Brown equalised for Cambridge in first-half stoppage time, when the home side’s player curled a bending strike into the back of the net.
Northampton responded by re-taking the lead after half-time, when a through-ball released Morias, and the Northampton man finished.
Cambridge were awarded a penalty during the second half when Brown was fouled, but from 12-yards, Brown couldn’t make the chance count when he struck the post.
It wasn’t long after that, however, that Cambridge equalised for a second time as Brown weighed in a free-kick that Taft converted.
Cambridge looked the likelier of the two teams to find the game’s fifth goal, but it looked as though proceedings would end level until Amoo intervened in time added on. A loose ball fell the attacker’s way, and he prodded home to decide the contest.