Craig Overton learns a day is a long time in the Championship

If a week is a long time in politics then a day is in county cricket. When Craig Overton walked off at lunch, he raised the ball with a proud smile to warm applause from the crowd after returning career-best figures of 7 for 57; just under six hours later, he trudged back with Somerset leading by 71 runs with two second-innings wickets in hand after being cleaned up by the second ball he faced.

Overton would strike again with his final ball to take his sixth wicket of the day and eighth of the match, having Nick Browne caught at midwicket, but Essex need only 81 more runs tomorrow to complete their win with nine wickets in hand. "It has to be perfect for us," Overton said. "If we can get Chef [Alastair Cook] out early we've got a chance but if he bats for half an hour, it's going to be difficult."

Somerset lost their opening game of the Championship season inside eight sessions and will lose their second inside seven, barring an Easter weekend resurrection. Damningly, Essex have not been at their best - they added only 71 runs to their overnight score, 24 of them for the last wicket - but should still be home in time to beat the Bank Holiday traffic.

It was Shane Snater, their Dutch-Zimbabwean seamer, who ran through Somerset on the second afternoon, taking the sixth five-wicket haul of a fifteen-match first-class career. Snater's claim to fame for most of his career has been that he is the cousin of Jason Roy but he has been a hugely dependable player since breaking into Essex's Championship team last season.

His emergence has allowed Essex to rotate their main three seamers (Sam Cook, Jamie Porter and either Peter Siddle or Mark Steketee) without any obvious drop-off in quality. Wearing a Karate Kid-style white headband, there was no great mystery in his craft as he nipped the ball both ways on a helpful pitch; Somerset's batters were obliging, gifting him several wickets, but his nip-backer to kiss James Hildreth's off stump was a beauty.

"He's given us extra depth within the squad," Anthony McGrath, Essex's head coach, said. "He was predominantly a white-ball bowler who wasn't really near the red-ball team but last year he made strides; he got into the team and his record was excellent. He can swing it, but he nips the ball both ways and he's always challenging the batsmen's defence. If you can do that - particularly in April - then you're going to be in the game.

"There's been some good bowling on show," he added. "The batsmen will say they could have played better but a lot of them have been got out. We've not seen many straight drives; people who haven't driven have been the most successful. It's been a strange old game… the ball has continued to move pretty much all the way through it."

For Somerset's batters, this was an innings that has become all too familiar, their tenth total of 181 or fewer in their last six Championship matches dating back to the start of Division One in August last year. This was a tough pitch - Overton admitted it felt like a different sport to the one he had played for England in the Caribbean last month - but some shots were unforgivable: Lewis Gregory top-edged a mow across the line to long leg, and Steven Davies lost his off stump trying to slap Steketee through cover after a breezy 51.

Tom Abell, their captain, will already be preparing his latest attempts to explain their inability to bat for long periods. He may point to the absence of the injured Tom Banton and George Bartlett, but neither of them averages 30 in first-class cricket; the truth lies in a crisis of confidence and a young batting line-up struggling to cope with the demands of top-division Championship cricket.

Following his dismissal today, edging a ball on a fifth-stump line behind off Steketee, Abell has 104 runs in his last 12 first-class innings for Somerset, dating back to their first Division One game at the end of last season. For all his qualities as a leader and a statesman, that form should be enough to pour cold water on the left-field suggestions that he could come into England's Test team as captain this summer.

After Cook had poked the first ball of the day to slip off Peter Siddle, Overton bowled two impressive spells in completing his seven-for, and looked like a different bowler to the one who had toiled on a flat pitch in Antigua last month. "Obviously this wicket has a little bit more pace and zip in it, so you feel more in the game as a seamer," he said. "The basics are still the same and I didn't quite get them right in the West Indies, but I did today."

He continues to manage a shoulder problem that has nagged away at him - "unless I have surgery, it's something that I'm going to have to deal with for the rest of my career," he said - but was rewarded for bowling a fullish length, with all seven of his wickets either bowled, lbw or caught in the cordon.

His dismissal of Browne in the penultimate over meant that the same two batters - the two Cooks, Alastair and nightwatchman Sam - are not out overnight again; they will return after a 19-wicket day with victory in their sights. Somerset, meanwhile, look doomed to a sixth consecutive Championship defeat for the first time since 1960.