James Maddison's sensational goal inspired Leicester to sink 10-man Watford.
The midfielder's first-half volley, finishing off a flowing break, sealed a 2-0 win for the hosts at the King Power Stadium.
It capped a turnaround for Maddison after he was sent off for diving in last weekend's 1-1 draw at Brighton.
Jamie Vardy's early penalty put the Foxes in control and, with Isaac Success and Andre Gray wasting Watford's best chances, the Hornets were well beaten - having Etienne Capoue sent off late on.
The Foxes leapfrogged them in the table and now sit seventh with Watford - who have won just two of their last 10 games - slipping to 10th.
The Hornets began brightly enough and Abdoulaye Doucoure saw an effort deflected over but they never recovered from Vardy's 12th-minute penalty.
Ben Chilwell slipped Vardy through and the striker nipped in ahead of Ben Foster, only for the goalkeeper to take him down.
Vardy had scored just once at the King Power Stadium this season but he confidently sent Foster the wrong way from the spot.
Since the start of 2014-15 Vardy has won 14 penalties in the Premier League, more than any other player.
Watford had won just once in their previous 11 trips to Leicester and their task got harder after 23 minutes when Maddison brilliantly made it 2-0.
The Foxes rode out brief Hornets pressure before hitting the visitors on the break as Maddison found Vardy.
The forward spun and fed the galloping Marc Albrighton and his pinpoint cross found Maddison, who had continued his run.
His exquisite first tough brought the ball down and he juggled past Adrian Mariappa - who got a touch - before volleying into the bottom corner from 18 yards.
It was the 22-year-old's first goal in over two months and redemption following his dismissal at Brighton.
Leicester were comfortable and Demarai Gray fired wide 10 minutes before the break before Success should have pulled a goal back.
The striker broke away with Gerard Deulofeu and wriggled goalside of Nampalys Mendy - only to shoot wastefully over with just Kasper Schmeichel to beat.
Watford tried to rally after the break and Ricardo Pereira denied Success a certain goal when he reached Deulofeu's cross ahead of the striker.
Roberto Pereyra also shot wide after 54 minutes in his last action before he was replaced by one-time Leicester target Troy Deeney.
Demarai Gray hammered against the outside of the post after Pereira's good run but, despite Watford's improvement since the break, the Foxes maintained a degree of control.
And with 17 minutes remaining Andre Gray blew Watford's best chance of rescuing the game when, unmarked, he missed his kick following Success' knockdown.
Capoue then compounded Watford's woes when he was dismissed a minute from time after a two-footed challenge on Kelechi Iheanacho.