Sean Dyche's Everton reign got off to a flying start as James Tarkowski's header handed Premier League leaders Arsenal a surprise 1-0 defeat at Goodison Park.
Everton looked revitalised in their first outing under the former Burnley boss, and it was two of his former Clarets players who combined for the winner – Tarkowski powering Dwight McNeil's corner home on the hour.
Arsenal were kept at arm's length by Everton during an unusually disjointed display, with the deserved victory dragging the Toffees – at least temporarily – out of the relegation zone.
Having suffered just their second league defeat of the season, the Gunners could see their lead at the summit cut to two points when title rivals Manchester City face Tottenham on Sunday.
Despite Everton starting strongly at a boisterous Goodison Park, Arsenal missed the first clear chance on the half-hour mark, Eddie Nketiah firing wide following excellent work from Bukayo Saka.
Dominic Calvert-Lewin somehow failed to slide home Amadou Onana's low delivery three minutes later as Everton threatened, before the unmarked Abdoulaye Doucoure headed McNeil's cross wide.
Conor Coady then made a vital goal-line clearance from Saka's volley, before Calvert-Lewin almost found the top-left corner with a looping header as an entertaining first half ended level.
Visiting captain Martin Odegaard blazed over from a good position after 59 minutes, and Arsenal were punished a minute later as Tarkowski found the bottom-right corner with a fine header from McNeil's right-wing corner.
Arsenal introduced January additions Jorginho and Leandro Trossard in search of a leveller, but the latter's 20-yard attempt, saved by Jordan Pickford, was as close as they came as their title hopes suffered a huge blow.