Pakistan leg-spinner Yasir Shah took all three wickets to restrict the West Indies to 97 for three in reply to the tourists' first innings total of 376 at lunch at Windsor Park in Dominica on Friday.
On a pitch offering little encouragement for the faster bowlers, Shah's role as both a stock bowler and premier wicket-taker were in evidence as he remained a perennial threat through an extended morning session in which he accounted for 11 of the 33 overs bowled.
Entrusted with the ball at the start of the day by captain Misbah-ul-Haq, the premier spinner did not disappoint, breaking a 43-run opening partnership between Kraigg Brathwaite and Kieran Powell.
Attempting to heave a delivery over the midwicket fence, Powell's miscued shot was well caught by Azhar Ali running in off the boundary to send the left-hander back to the pavilion for 31.
With Brathwaite plodding along in his usual stoic manner at the other end, new batsman Shimron Hetmyer sought to seize the initiative from the bowlers. His intentions were clear when he hoisted Shah for the only six of the innings so far.
But the bowler exacted swift revenge as an original "not out" verdict by standing umpire Bruce Oxenford for an appeal for a leg-side catch by wicketkeeper Sarfraz Ahmed was overturned on review when television replays revealed a faint touch of the ball onto the batsman's glove.
There was no doubt though to Ahmed's second dismissal of the morning as Brathwaite, who had grafted his way to 29 off 123 deliveries through three-and-a-half hours, pushed forward to Shah in the last over before the interval and edged a catch high to the wicketkeeper's right.
Shai Hope (15 not out) is expected to be joined in the middle by fellow-Barbadian Roston Chase when play resumes. Shah has now taken 20 wickets in the series.
On second day of the test, Azhar Ali's 14th Test century anchored Pakistan to a first innings total of 376 as the tourists batted with exaggerated care.
Pakistan's innings occupied all of 146.3 overs at a scoring rate of just over two-and-a-half runs per over, a puzzlingly pedestrian rate of progress on a benign pitch, especially as victory would give Pakistan their first-ever Test series win in the Caribbean in eight attempts.
After crawling along in the morning session, when only 58 runs came off 28 overs in two-and-a-half hours of play for the loss of Younis Khan's wicket, the tourists attempted to accelerate with captain Misbah-ul-Haq releasing the shackles of virtual strokelessness in getting to 59. Wicketkeeper-batsman Sarfraz Ahmed was by far the most enterprising of all in the Pakistan batting line-up though, being ninth out for 51 off 73 balls.
Off-spinner Chase was the prime beneficiary of the visitors' belated attempt at acceleration, finishing with four for 103.