David Amoo struck in stoppage time to earn Cambridge a thrilling 3-2 victory over Northampton.
Amoo fired a loose ball into the far corner in the fourth minute of time added on to secure a third successive win and send the Abbey Stadium into raptures.
They had needed to come from behind twice, first through Aaron Pierre's fierce finish on 27 minutes after Will Hoskins had hit the bar with a header.
Jevani Brown's beautifully-curled equaliser, bent into the far corner with the outside of his left foot on the stroke of half time, was negated by Junior Morais putting Northampton back in front on 48 minutes.
Brown then won and missed a penalty, hitting the post, five minutes later.
He made amends when his free-kick was perfect for George Taft to head home an equaliser for Cambridge on 64 minutes.
The U's dominated the closing stages before securing a massive winner in stoppage time, meaning Colin Calderwood's side climb to within a point of their opponents in the table.