Alexis Sanchez' hat-trick helped Arsenal end Leicester City's unbeaten start to the season as they claimed a 5-2 Barclays Premier League victory at the King Power Stadium.
The Arsenal forward had not scored this season, but was on top form as Arsene Wenger's men ultimately cruised to victory.
Leicester, who came from behind in their last four league fixtures, took the lead this time through Jamie Vardy's fourth goal in as many league matches 13 minutes in.
Arsenal fought back to be in front when Sanchez nudged in from close-range, after Walcott's 12th goal in his last 13 Barclays Premier League starts had levelled the scores.
Sanchez capped a stunning Arsenal move to head in his second after the interval, before claiming his hat-trick with a sumptuous strike from distance.
Vardy's sixth goal of the season rounded off a fine individual performance to make it 4-2, only for Olivier Giroud, a substitute, to add another for Arsenal in stoppage time.
Leicester would have been behind early on but for a goalline clearance from Ritchie De Laet, but responded well and nearly went ahead when Jeffrey Schlupp drew a fine save from Petr Cech.
Moments after hitting a post with a scuffed effort, Vardy lit up the match as he latched on to Danny Drinkwater's raking pass and drifted in from the left to curl a superb finish beyond Cech.
The England forward was just inches away from a second five minutes later, his header clipping the top of the crossbar.
Arsenal pulled level from the resulting counter-attack, Santi Cazorla sliding through to Walcott, who raced in behind Robert Huth to squeeze in off the left upright.
Wenger's men completed the turnaround shortly after the half-hour as Hector Bellerin's drilled cross was missed by Walcott, but Sanchez was on hand to tuck home from close range.
Leicester captain Wes Morgan could have restored parity on the stroke of half-time, but failed to apply the finish after connecting with Marc Albrighton's pinpoint free-kick.
Arsenal's goalscorers combined well after the interval, Sanchez latching on to Walcott's flick, but his strike was deflected wide.
Sanchez doubled his tally just prior to the hour, ghosting in from the right to beat Leicester's offside trap and head in Mesut Ozil's cross past the despairing reach of Kasper Schmeichel.
The Chilean had his hat-trick with nine minutes remaining, floating in from the left before firing into the bottom-left corner from 25 yards.
Although Vardy curled in a second for the hosts, Giroud swept in from Nacho Monreal's cross to add a fifth, as the visitors doubled their tally of league goals for the season in one outing.
Leicester City manager Claudio Ranieri: "It was difficult at the beginning and difficult at the end. We touched the post twice and that was our best moment.
"Arsenal are dangerous on the counter attack. The first half was good and open but at 3-1 it was difficult.
"We shoot at goal a lot of times but Petr Cech is Petr Cech. I hope if we could hold at 2-1 we could force it until late in the game but Alexis Sanchez scored early.
"The second half was then finished. We must begin again now and repeat this start to the season.
"We must show character in the next match."
Arsenal manager Arsene Wenger: "We created many chances and I felt a game like this confidence was coming. I think we always looked dangerous.
"We managed to come back from 2-1 and after that I feel we dominated the game.
"Alexis was waiting for a goal and he's not used to not scoring for so long so it was important for him to score."