Jonathan Joseph inspired the biggest upset of the season as London Irish thrashed unbeaten leaders Northampton 39-17 at the Madejski Stadium.
The England centre touched down for the opening try and he played a key role in scores by David Paice and Topsy Ojo as London Irish turned the Premiership table on its head.
Jamie Gibson wrapped up the Exiles' first bonus point of the season with their fourth try to cap another outstanding individual display.
By the time Ken Pisi and then Phil Dowson scored late consolation tries for Northampton, the Saints already trailed 33-3 and their goose had been well and truly cooked.
Reigning champions Harlequins missed the opportunity to go back to the top of the table as Exeter celebrated their 50th Premiership match with a try-scoring bonus point 42-28 victory at Sandy Park.
The triumph was sealed by three tries in the final 20 minutes of the match, with Jason Shoemark (64, 67) and Sireli Naqelevuki (78) the players to cross.
Brett Sturgess scored a first-half try for the Chiefs but it was Harlequins who went into the break with a an 18-16 lead thanks to efforts from Nick Evans, who also kicked a conversion and two penalties, and Ugo Monye.
Ben White crossed early in the second period to put Exeter back in front and although Karl Dickson responded for the visitors, Exeter's late charge proved decisive.
In Saturday's other game, Gloucester fought back from an alarming early deficit to make it five games unbeaten and extend Bath's miserable losing run at Kingsholm as they won 16-10.
Bath made a powerful start in pursuit of a first win on Gloucester soil since 2006 after fly-half Stephen Donald converted his own first-minute try and then kicked a penalty.
But Gloucester responded from 10-0 adrift through two Freddie Burns penalties, before he added the extras to full-back Rob Cook's 50th-minute touchdown and then slotted a late drop-goal.
On Friday night, scrum-half Ben Youngs scored the decisive try on his return from injury as Leicester came from behind to condemn Sale to their sixth consecutive defeat with a 20-8 triumph.
It was Sale who dominated the first half despite holding just an 8-6 lead through Rob Miller's unconverted try and a Nick Macleod penalty.
Leicester's George Ford, deputising for Toby Flood, responded with two three-pointers in what was initially a disappointing team display.
But they were revitalised in the second period and scored 14 unanswered points through the boot of Ford and a try from Youngs.