Left-arm spinner Taijul Islam ended with figures of 6 for 163 - his third Test five-for - as Pakistan lost their last five wickets for 34 runs, but the damage had already been done. Leading by 205 runs at the start of the day, Sarfraz Ahmed and Asad Shafiq extended that dominance with a 126-run stand for the sixth wicket. Both batsmen missed out on centuries but Pakistan's total propped up to 628, their best against Bangladesh, and the lead to 296.
With the field spread out, Sarfraz and Shafiq rotated the strike with ease and added 57 runs off 70 balls on the fourth morning, a period that contained only two boundaries. But the tone had been set in the second over, when Shafiq came down the pitch to loft Shakib Al Hasan over mid-on for three runs.
The first boundary - a powerful sweep by Sarfraz off Taijul - brought up the century of the partnership in 138 balls. Sarfraz, though, perished at mid-on off debutant Mohammad Shahid for 82. Shafiq, too, chipped one back at Shakib, giving the bowler his first wicket in his 36th over. The rest were cleaned up by Taijul.
A couple of rippers from Taijul in his first two overs turned and bounced from the middle-and-leg line to beat the outside edge. But rather than being the early morning ray of hope after two days of toil, those deliveries spelt the challenge awaiting the Bangladesh batsmen over the remaining sessions.
Keeping a close eye on them was Imrul Kayes, who had been squatting behind the stumps as a substitute wicketkeeper for more than 100 overs after Mushfiqur had injured his right hand. Eight overs into the day Kayes, in an act of self-preservation, passed on the gloves to Mahmudullah.
Donning the role for the first time in international cricket, Mahmudullah was perhaps not aware of the job responsibilities. Sarfraz blocked in front of the pitch and checked behind to see if Mahmudullah was coming forward to pick up the ball, but then went on to lob it towards the bowler.
That generosity was not expected from the Pakistan bowlers. As Bangladesh came to bat for a brief period before lunch, Junaid Khan asked for a review first ball after an inswinger thudded into Tamim Iqbal's pads. The replays showed Tamim had a narrow escape, with the ball grazing the leg stump.
Devashish Fuloria is a sub-editor at ESPNcricinfo