New Surrey captain Graeme Smith was dismissed for two in his first innings for the county as Somerset enjoyed the better of a rain-shortened day two at the Oval.
The South Africa Test skipper was undone by Peter Trego's bowling in the third over of Surrey's reply to Somerset's first-innings effort of 384.
Surrey closed on 98-4, still 286 adrift, after Somerset returned from a rain delay of more than three hours to claim the wickets of Vikram Solanki and Zander de Bruyn in successive overs late on.
James Hildreth at second slip took a low catch to send Smith on his way and then, two deliveries before the scheduled lunch interval, Arun Harinath (5) also picked out Hildreth in the cordon off Alfonso Thomas (1-21).
Left-hander Rory Burns (43no) and former England international Solanki - making his Surrey home debut - took the score through to 66-2 before rain arrived at 2.30pm.
Mopping up started just before 5pm allowing umpires Jeff Evans and Richard Kettleborough to restart proceedings at 5.45pm for a further 16 overs in the day.
In tandem with Burns, Solanki added 56 inside 20 overs before the former Worcestershire batsman fell for 30 late in the day.
In aiming to hook the first ball of the evening from Jamie Overton (1-10), a long-hop loosener, Solanki got a thick bottom edge and dragged the ball onto off stump.
In the next over and with the floodlights already on, De Bruyn (1) pushed hesitantly at a good length ball from Steve Kirby (1-33) and deflected it on to leg stump.
At the start of the day Surrey bowled another 12.4 overs and needed a further 50 minutes to remove Somerset's two remaining first-innings wickets. Jade Dernbach finished with 5-57.