Leinster Lightning fought back on day two of the Three-Day Inter-pro as they finished on 320-4 in reply to the Northern Knights' 440-9 declared.
Ireland batsman Andrew Balbirnie was unbeaten on 81 for Leinster with Jack Tector earlier hitting 87 and Stephen Doheny notching 50 at Pembroke.
After starting the day on 415-8, the Knights added 25 before declaring after Mark Adair was out for 91.
James McCollum top-scored with 93 for the Knights.
Adair's innings included three sixes and 12 fours before he was caught and bowled by Josh Little.
In reply Lightning were soon relishing the conditions although they didn't force the pace and the run rate was a lot less than their opponents.
Tector and Doheny put on 112 for the first wicket while Balbirnie was still undefeated on 81 after his patient 171-ball knock.
The game resumes in on Thursday morning.
First innings 440-9 dec (109.3 overs) J McCollum 93, M Adair 91, MP Ellison 64, H Tector 52; K McCollum 5-32, M Adair 3-33; S Singh 3-75, J Little 3-95
First innings: 320-4 (96 overs) J Tector 87, A Balbirnie 81 no, S Doheny 50, S Getkate 1-41