With a draw no good to either side, both played positively in Lincoln and Town were narrowly defeated by nine runs, losing with four balls remaining as they valiantly attempted to chase down a target of 233 for victory.
Lindum and Grimsby possess some of the county's best young batting talent and stroke play was in plentiful supply.
The home side won the toss and batted first, with Pierce Morley Barnes (66) and Karanjit Bansal (28) putting on 65 for the first wicket.
Bansal played a poor shot and was bowled by Lee Charlton.
Pierce Morley-Barnes was joined by Alex Hornsby and they added 67 for the second wicket in 15 overs.
Morley-Barnes played some lovely drives through the offside and his 66 came off 104 balls and included 10 fours. He was eventually bowled by off spinner Gihan Perera as he tried to cut him.
Having looked comfortable at 132 for one, Lindum's middle order struggled and they lost their momentum.
Gary Tillison got one to bounce and wicketkeeper Steve Crossley took a good catch to dismiss Geoff Middleton for four.
Luke Robinson quickly departed, also for four, as he edged Perera to Richard Antcliffe at slip.
Perera then had Harry Dunn caught and bowled for 10 and, when Hornsby departed for a good 65 from 85 balls, Lindum were 192 for six with five overs left.
Tillison dismissed Hornsby as he attempted to make room and he deserved this second wicket for his sterling efforts with the ball. The fast bowler produced a wholehearted display and finished with two for 59 from his 17 overs. He was well supported by Perera who took four for 67 from 14 overs.
Lindum's innings needed a late boost and it got this when Qasim Memon (26) and skipper Matt Rutherford (18no) put on 40 for the seventh wicket in the final five overs.
Grimsby's ground fielding was at times scrappy and not up to its usual high standards as Lindum finished on 232 for eight from their 50 overs.
Grimsby's reply began badly when Antcliffe was dismissed lbw for a duck by Stuart Turner.
Neil Snell looked in good form as he raced to 30 from 29 balls. He and Nigel Fanthorpe added 46 for the second wicket in only eight overs.
Rutherford bowled Snell with a good quicker ball and then Fanthorpe had a rush of blood and was stumped by Dale Christie off the left-arm spinner.
At 52 for three Grimsby needed to rebuild and they did this with Perera and Scott Harneiss putting on 70 for the fourth wicket in 23 overs.
Perera was forced to battle early on as Lindum's spinners bowled well in tandem. He survived a stumping appeal and was dropped at point on 16. He showed great character though and made his highest score of the season, 71 from 101 balls.
Harneiss made a gritty 26 from 70 balls.
With Grimsby 133 for five with 12 overs left, a victory looked highly unlikely.
Perera was joined by Crossley, who looked like a man on a mission. He decided to take on the spinners and smashed 39 from only 30 balls. He hit a massive six over square leg off spinner Bansal.
Perera too began to step up the pace and Lindum began to look nervy.
It took two outstanding catches to swing the game back the home side's way. Bansal took a brilliant caught and bowled to dismiss Perera and then Rutherford took a catch over his shoulder to remove Crossley off the same bowler.
Tillison refused to give up hope and hit a trademark big six as he added 18 from 16 balls.
Sadly for Grimsby he was bowled by Bansal, who finished with five for 80, and a fascinating game was over. Grimsby were all out for 223, Rutherford finishing with three for 47 from his 17 overs.