The Walking Dead season 8 episode 1 'Mercy' review: Taut, thrilling and unsettlingly optimistic

*Spoilers for season 8 episode 1 follow*

To non-fans, it's perhaps inevitable to assume that after seven seasons and 99 episodes The Walking Dead has outstayed its welcome since debuting back in 2010 - a notion perhaps matched by even the most dedicated fan following the last year’s slower-paced run.

Concerns for season eight were, as a consequence, rather rife but cast them aside: the US series has returned with a taut, thrilling and disarmingly optimistic outing that will silence any questions surrounding the relevancy of a long-running series in a time filled with so many new ones.

The premiere, titled 'Mercy,' features the usual - action, smirk-inducing character interactions and on-the-nose dialogue about “reshaping the world” and “hopeful tomorrows.” The threat of Negan (Jeffrey Dean Morgan) looms large (it's only been a few weeks for our characters) and if season seven was our introduction to the new world once teased by Jesus (Tom Payne), this premiere is an introduction to something else altogether - a season of payoff.

This episode sees Rick Grimes (Andrew Lincoln) and company bring the war to the Saviours - the first half showing the army comprised of Alexandria, the Hilltop and the Kingdom preparing for battle (rabble-rousing speeches, makeshift armoured cars) with the remainder devoted to evening the playing field; if Morgan’s wisecracking bad guy seemed an insurmountable foe as he sped out of Alexandria last season, he ends the episode a wounded beast, his compound in tatters and - perhaps most dangerously - his ego dented.

Has everything been building to this premiere? Perhaps not, but it certainly feels like the series has been bolstered by a renewed sense of purpose since leaving screens in March. While paying homage to past seasons with callbacks to scenes from far simpler early days (it’s been 100 episodes, after all), 'Mercy' is refreshingly far more versed in where these characters are headed as opposed to rehashing the reasons why they're at war with the Saviours.

It’s this which subtly injects the episode with reasons to keep you watching, touching upon the fate of Grimes - the show’s hero - with a series of ambiguous scenes that will no doubt emerge as the episode’s biggest talking point: flashforwards (or are they dream sequences?) show an older version of the character at an unspecified time in the future. His hair is greying, and he's hobbling around with a cane while wearing a dressing gown - a leader no more. Details are drip-fed to viewers: he's still living with girlfriend Michonne (Danai Gurira), son Carl (Chandler Riggs) as well as baby-no-more Judith. If 'Mercy' hammers home the fact that Rick's tenure as group leader is drawing to an end, these scenes underline it.

'Mercy' hints that season eight - while showing us the much-hyped All Out War comic book arc - will inadvertently serve as an audition for Rick's replacement ("this is your show," Michonne says to Carl at one stage, while another moment sees Rick tell a still-pregnant Maggie he plans on "following" her lead once Negan is defeated) which is a decidedly risky game-plan eliminating much tension regarding his fate.

If the episode may not be the series as its strongest, it’s certainly The Walking Dead stronger than it has any right to be eight seasons in returning with an assured 100th episode that adeptly weaves between the large ensemble (last count: 19) despite minimal screen time for plenty: Daryl, Carol, Morgan and Tara have been bunched together while Eugene - seemingly, at least - remains an ally of Negan's

Most shows at this stage would be crawling towards cancellation but after 100 episodes, The Walking Dead has regained its stride with heart-stopping aplomb.

The Walking Dead season eight continues Sundays in US on AMC with the UK premiere arriving the following evening on FOX at 9pm as well as on NOW TV - watch the trailer for episode two, 'The Damned,' here.

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