A's 6, Mariners 5. Seattle sent Bob Stoddard, who is pretty unimpressive. Oakland's response was Steve McCatty, who had once been impressive but was not any longer.
Both pitchers allowed scoring in the first inning. McCatty yielded a run on singles to Jack Perconte and Steve Henderson, which were followed by a pair of flyouts that sent Perconte to third and home, respectively. Stoddard gave up considerably more, starting with one-out walks to Dwayne Murphy and Joe Morgan. A wild pitch sent them to second and third, and Dave Kingman then singled them both home. Bruce Bochte walked with two outs, and Mike Davis grounded to short, where Spike Owen committed an error that allowed both runners to score and put Oakland ahead 4-1.
McCatty threw a 1-2-3 second, while Stoddard once again walked Murphy and Morgan, but this time left them on. Seattle picked up a run in the third when Owen singled, stole second, moved to third on Perconte's single, and scored on Henderson's sac fly. Carney Lansford doubled in the bottom of the third, and Murphy singled in the fourth, but Stoddard stranded each of them in turn.
The Mariners further narrowed the gap in the fifth when Henderson cracked a two-out solo homer. Stoddard was spotless in the fifth and sixth, while McCatty allowed an Al Cowens single and steal in the sixth only to see him thrown out trying to score the tying run on Darnell Coles's subsequent hit. That run would be delayed by only one inning. Tom Burgmeier succeeded McCatty in the seventh and promptly allowed a leadoff triple to Owen, Henderson walked and Alvin Davis reached on an everyone-safe fielder's choice (they presumably threw home, because Owen stayed at third) to load the bases. Gorman Thomas greeted Bill Caudill with his second sac fly of the game to even the tally at 4 runs apiece.
Paul Mirabella relieved Stoddard in the bottom of the seventh, and with two outs, allowed a Morgan single. Roy Thomas took the mound in Mirabella's place and saw Morgan move to third on a steal-and-error; Thomas then hit Kingman with a pitch and walked Lansford to load the bases before Bochte fouled out to end the inning.
Caudill managed a perfect eighth, and the A's finally scored again in the bottom of the inning. Davis led off with a single, but was quickly picked off. Mike Heath followed with a walk, however, and pinch hitter Davey Lopes promptly doubled him home. Lopes stole his way to third, but the top of the order could not bring him home; they would regret that failure an inning later when Seattle re-tied the score on singles by Perconte and Henderson and a Davis sac fly (on which pinch runner Phil Bradley went first-to-third, which is... unusual).
The Mariner celebration was short-lived. Morgan led off the bottom of the inning with a walk, stole second, and moved to third on a single by pinch hitter Garry Hancock. Mike Stanton relieved Thomas and retired Lansford, but Bochte followed with a walkoff single.
Joe Morgan was 40 years old when this game was played, and in his last major league season. There is no way he should still have had the leadoff-type hitting chops he displayed: three walks, two steals, and two runs, including the game winner. Between Morgan and his former positional and divisional rival, Davey Lopes, the A's had just enough to counteract the production difference between the two Hendersons: Rickey went 0 for 5 with three strikeouts (and was not mentioned once in the recap), while Seattle's Steve went 3 for 4 with a homer, 2 RBI, and a key part in the game-tying rally in the ninth, good for a season-high +.391 WPA for him.
Combine those features with a game that also included a tie that was either broken or re-forged in each of the last three half-innings, and you've got yourself a banner nine-inning effort.