Sheldon Cottrell smashed a six off the penultimate ball to seal a series win for West Indies over Ireland with a one-wicket win in Bridgetown.
The second ODI went down to the wire with the home side needing five runs from the final six balls with one wicket in hand to take an unassailable 2-0 lead.
Mark Adair conceded three in the first four balls, during which the match could have been wrapped up twice.
The third umpire was summoned to judge a run out when Cottrell was caught short of his crease, but the ball was considered not to be in Adair's hand when the bails were dislodged.
The next ball and Cottrell's partner Hayden Walsh did not go for a second run while Cottrell was well on his way, but Ireland failed to capitalise from the mix-up.
Needing two from two, Cottrell sent it over the covers and the Kensington Oval crowd into raptures.
Ireland smelt blood at the mid-point in the innings, sending Nicholas Pooran, Romario Shepherd and dangerman Keiron Pollard back to the sheds within three overs.
But the Windies moved on from 148 for seven to 200 for eight as Walsh (46) and Khary Pierre (18) combined for a 52-run stand, with the late wicket of Alzarri Joseph setting the scene for a tense finish.
After being dismissed for 180 in the series opener, Paul Sterling made sure Ireland would pose a much tougher proposition this time.
He led the way at the top of the order with a 79-ball 63, although his dismissal left the away side on 129 for four.
Kevin O'Brien put the West Indies on the back foot with a rapid 31 while Simi Singh's patient 34 took Ireland over the 200-mark and they set the hosts 238 for victory.
As in the first match, Joseph finished with figures of four for 32 - leading to a second consecutive man of the match award - and Sheldon Cottrell chipped in with three scalps.
"The squad are hugely disappointed, we left pretty much everything out there," said captain Andrew Balbirnie afterwards.
"Unfortunately we didn't perhaps get the rub of the green at the end, but I can't fault the lads and the effort they put in. That was what I asked from them before the game, and between innings - to go out there and make it as hard as possible for the West Indies to chase the target and I think we did that.
"It's a couple days before the next game and the guys are excited to get going again, particularly now we realise how close we came to beating such a good team like the West Indies.
"It's important that we recover well today - we have a short flight to Grenada, but if we can recover well, have a good training session tomorrow and get what we need done then I have no doubt we can turn around this result on Sunday."