Ben Slater hit a half-century as Derbyshire and Somerset’s compelling LV= County Championship clash at Taunton remained on a knife-edge at the end of day three.
The visitors closed on 127 for four, needing a further 117 to win on a pitch offering considerable turn and lift. Slater had appeared to have made Derbyshire slight favourites but spinners Piyush Chawla and Jack Leach each took two wickets to set up a tense final day between the relegation battlers.
Earlier, Somerset had added 207 to their overnight second-innings score, setting a victory target of 244 after trailing by 195 after the first innings.
Nick Compton fell five short a hundred, while Lewis Gregory hit a maiden half-century and Craig Meschede contributed 33 before being run out.
Tony Palladino and David Wainwright finished with three wickets each but Derbyshire had let a position of dominance disappear and faced a tough task.
They looked to be in trouble when young left-arm spinner Leach struck twice to reduce them to 53 for two, removing Paul Borrington and Wayne Madsen.
But Somerset's cricket then fell apart with some sloppy ground fielding, while wicketkeeper Craig Kieswetter found the turn and lift extracted by Leach and Chawla too much for him.
The 25-year-old, who boasts 46 one-day international and 25 Twenty20 international appearances for England, conceded 22 byes - making 40 in the match - forcing skipper Marcus Trescothick into some bizarre field changes.
Slater was in the mood and form to capitalise, hitting 10 fours in his 117-ball innings before falling to a sharp catch by Alex Barrow at short-leg with the total on 117.
Nightwatchman Palladino then departed to a slip catch by Trescothick off Chawla in the closing over of the day, leaving all results possible.
If the visitors need a rock around which to build the rest of their innings he is there in the shape of Shivnarine Chanderpaul, who is unbeaten on 20 after his now occasional leg-breaks brought him 2-32 in Somerset's second innings.
Compton showed what can be achieved on such a pitch with good technique and application. Unbeaten on 64 overnight, he batted for four hours and 19 minutes in all, hitting just eight fours from 205 balls, before being bowled by Palladino.
It was a memorable day for Gregory, who eclipsed his previous best first-class score of 48, made against Warwickshire in 2011, by reaching 52.
He shared a last wicket stand of 39 with Leach, which could yet prove crucial, before his five-over new-ball spell did not yield a single run.