Stefano Okaka scored his first goals for Watford as the Hornets recorded their first win over Everton since 1987.
The Italian striker, signed over the summer, cancelled out Romelu Lukaku’s opener with an excellent backheeled finish, then scored the Hornets’ third of the game after Sebastian Prodl’s header put the hosts in front.
Lukaku pulled one back late on to ramp up the pressure, but Watford held on and claimed three points which moved them ahead of their opponents - and into the top half of the table.
The early stages were dominated by the visitors, Deulofeu causing chaos in the area with a cross which Gomes had to punch clear, before the Brazilian keeper had to snuff out a series of later attacks.