Perhaps Mike Flanagan's three-hit victory over the Cleveland Indians in the chill and mist of Memorial Stadium today was just a misleading illusion. After all, in the past three seasons the Baltimore Orioles' left-hander has had occasional wins like this day's effortless 6-1 triumph, games when he seemed to regain the form of 1979 when he won the Cy Young Award.

Through three seasons of arm-trouble and personal miseries, Flanagan has insisted that, with enough persistence and enough rehabilitation of his overworked shoulder, he would regain the fast ball that elevated him from good to great.

This afternoon, before 36,430 fans, Flanagan turned "Bat Day" into Pitch Day with an intimidating, power-pitching performance, holding Cleveland to three singles. "If this is any indication, I guess he's back," said Andre Thornton, the Indians' cleanup man who drove in Cleveland's run with a sacrifice fly and who, over the first 8 2/3 innings, had the visitors' only clean hit. "That's as well as I've ever seen him throw."

Flanagan (2-0) is famous for having the biggest-breaking southpaw curve of any American League starter, but the real key to whether he's a 15- or 20-game winner is his fast ball. When he can throw it for strikes at the knees--time after time--with impunity, he moves into the 23-9 class of '79; when he must change speeds and pray for breaks, he's the gritty fellow who's battled his way to a 40-30 record in the past three years.

This afternoon, Flanagan threw 107 fast balls out of 131 pitches.

"I just threw the curve balls to throw 'em," said Flanagan, who turned lefty Bake McBride inside out on two breaking ball strikeouts. "The way the fast ball was moving all over the place, I could have thrown nothing else."

When did he last pitch a low-hit complete game in which he, basically, threw only heat?

"I can't remember back that far," he said, grinning.

This was the kind of day that any pitcher would love. The wind blew in from left. An injury to Toby Harrah (broken hand), plus Indian manager Mike Ferraro's decision to bench lefties Mike Hargrove (.091 career average against Flanagan) and Rick Manning, left Cleveland with a AAA quality lineup.

No sooner had the Indians scored in the first inning --on a walk to Miguel Dilone, a hit-and-run single by Manny Trillo and Thornton's fly--than Cleveland starter Bert Blyleven, making a comeback from elbow surgery, self-destructed.

The Indians' right-hander, who has a curve even more embarrassing to hitters than Flanagan's, walked the first three Orioles he saw. Blyleven's 14th ball out his first 16 pitches rolled to the screen as a run scored. Eddie Murray scorched his next offering to center for a two-run single.

In the third, Murray, hitting .382, singled to center, then took second on John Lowenstein's hit-and-run ground out. That base meant a run when Jim Dwyer, starting for Ken Singleton who has a pulled back muscle, singled home Murray.

In the fourth, Blyleven was shocked by three hits, good for two runs, on three consecutive pitches. Joe Nolan singled, Al Bumbry doubled to the wall in the leftfield corner, and Dan Ford singled to left, raising his average to .448 (13 for 29). The Orioles (5-4) are now in first place in the AL East.

Some baseball lives go in cycles. Perhaps no one in baseball senses it more acutely than Flanagan. His life's graph was one long rising line until the day before the final game of the 1979 World Series. Then, his wife Kathy had the first of her two miscarriages. And of far less importance to Flanagan, the lost world title, came on top of a major sore arm to Flanagan.

Dr. Arthur Pappas says Flanagan had the narrowest escape from a (probable career-ending) torn rotator cuff than any pitcher he'd ever seen.

Flanagan attributes the problem to his own stubbornness ("I did it to myself") and former manager Earl Weaver's determination to leave him in games until he asked out--which he wouldn't do. "I'd do it differently now."

Through '80 and '81, Flanagan seemed distracted--far more concerned about his wife's health and state of mind, their chances of having a family--than his arm or his pitching; he tried, but, basically, he just didn't care.

The story of how the Flanagans came to have one of the first test tube children born in America--Kerry Ellen, now 8 months old--is well known. What isn't known, perhaps, is that all the other forms of fortune in Flanagan's life seem to have turned a corner simultaneously.

"We say it all changed when she became pregnant," said Flanagan today. "It was like that ended a drought from the seventh game of the ('79) Series. It was almost two years to the day. After that (the successful pregnancy), my arm started to improve. Dr. Pappas told me that the rehabilitation program would take two years and he was exactly right."

In '82, Flanagan pitched without pain. After his daughter's birth, he also pitched with renewed joy, ripping off a seven-game winning streak in the pennant race. Since her birth, Flanagan is 11-3, including a current streak of nine wins in his last 10 decisions. "It certainly feels like the luck has changed . . . I haven't felt so much as a twinge in my arm in a year and a half."

The last piece in the Flanagan puzzle is his fast ball. How often he'll have it back at his disposal and just how good it will be, neither he nor anyone else knows. But today, the Indians got a hint.

"I just poured it down the middle and it broke all over the place," said Flanagan. "I didn't know where it was going. It was really alive."

Just like the Flanagan of old.