Derbyshire paceman Tim Groenewald took a hat-trick and the prized wicket of England captain Alastair Cook as Essex were bowled out for 94 on day one at Chelmsford.
Cook was comfortably Essex's top scorer with 35 of an innings that saw four colleagues fall for ducks in the Division Two match.
Derbyshire bowlers Mark Footitt and Groenewald did all the damage with the ball, returning respective figures of 5-29 and 5-44.
In reply Derbyshire, whose first game was postponed last week after Tom Poynton was involved in a car crash in which his dad died, opened up a 45-run lead by posting 139 for five at stumps.
— Derbyshire CCC (@DerbyshireCCC) April 13, 2014
Jaik Mickleburgh was the first to go for Essex when he was bowled by Footitt, and Cook joined him back inside five overs later when his swift scoring was halted when he nicked Groenewald behind to Richard Johnson. Cook had found the boundary four times in a 46-ball stay.
England all-rounder Ravi Bopara lasted just 15 balls for three runs and headed back to the pavilion in the 20th over after he was caught in the slips by Wes Durston off Groenewald, becoming the first victim of the hat-trick.
Groenewald bowled Greg Smith and then had Ben Foakes snared lbw as the 30-year-old South African completed his feat.
James Foster, England spinner Monty Panesar and Tymal Mills made it to double figures for the home side in a dismal innings.
Essex medium-pacer David Masters took the first three Derbyshire wickets - removing openers Billy Godleman and Stephen Moore cheaply before snaring Wayne Madsen on 30 - but former West Indies captain Shivnarine Chanderpaul steadied the innings with a half-century.
Durston hit four fours before losing his wicket for 21 runs to Mills, with Chanderpaul, who reached 66 not out, and new batsman Johnson taking the visiting team to the close.