Nottinghamshire seamer Luke Fletcher took three wickets for no runs in the space of 22 balls to plunge Somerset into trouble on a rain-shortened third day of the LV= County Championship match at Taunton.
Fletcher removed Nick Compton and then sent back Craig Kieswetter and Peter Trego with successive deliveries as the hosts slumped to 81-6 in reply to 378.
Several rain breaks and a half-century from Craig Meschede (59) frustrated the visitors before Somerset closed on 188-9 - still 41 short of avoiding the follow-on - with 49 overs having been lost.
The hosts began the day on 70-1 and lost three wickets for two runs either side of the first rain delay. Chris Jones had his off bail removed by Andre Adams without adding to his overnight score of 37 before Compton and James Hildreth surrendered their wickets to poor shots.
Compton, on 34, chased a wide ball from Fletcher and lofted a catch to cover, while Hildreth had made only two when he carelessly top-edged a pull shot to fine-leg to give Adams a second wicket. That made it 75-4 and six runs were added before more rain set in at just before midday.
Play resumed at 2.35pm and Fletcher continued to weave a spell from the River End. He bowled two maidens to Kieswetter and then had him caught behind by Chris Read, diving to his right, for a single.
The next ball saw Trego push forward and depart to a regulation nick. Fletcher went on to complete a spell of 3-13 from eight overs either side of the rain interruption, with his runless spell extending to 29 deliveries.
Jos Buttler became the next Somerset batsman to throw his wicket away. After cruising to 23 with four fours, the England one-day player miscued a pull shot off Samit Patel and gave a simple catch to mid-on.
At 122-7, Somerset were still 107 runs short of avoiding the follow-on. But Meschede played positively to reach a 65-ball fifty, with six fours and two sixes, both sweetly timed over mid-wicket in the same Patel over.
Dockrell lent sensible support and by the time the players were forced off again at 4.50pm the pair had added 53, putting some of the earlier batsmen to shame.
An unlikely resumption was made at 5.55pm and in the second over Meschede was bowled off an inside edge by Harry Gurney.
It was too dark for Chris Read to persist with his seamers, but Patel had Dockrell caught off bat and pad for 23 before bad light ended proceedings at 6.20pm.