A grateful grad has sent professors packing, with few questions asked.

The rewards of teaching can sometimes seem intangible: modest pay, heavy demands, and only occasional expressions of gratitude from former students who are busy with their lives.

But at Whitworth College, a small, Presbyterian liberal arts school in a pine forest north of this city, one anonymous graduate has been saying thanks in a unique way.

The alumnus, who signs his notes only “M.M.” and thus is called the Mystery Man, since June, 1988, has provided 17 present and former faculty members with free vacations.

He also has given gifts, ranging from exotic foods to cameras and coffee grinders, to longtime teachers at the college.

The gesture has produced an electric boost of morale at Whitworth, a college of low pay, high ideals and a strong relationships with its 1,300 undergraduates.

“My first contact was a bolt out of the blue,” recalled Bob Bocksch, a chemistry professor. He was the first to be offered a trip by a Bremerton, Wash., travel agent representing M. M. “I thought it was a bunch of students playing a prank on me.”

Finally convinced when he received tickets and an itinerary, Bocksch went off on his first visit to the Hawaiian Islands and, he says, “had a marvelous two weeks.”

When the travel agent later offered him a second trip, he suggested a gift to a laboratory equipment fund instead. The donor sent $5,000, then insisted that Bocksch and his wife take a cruise last summer to Alaska as well.

In a subsequent letter, the donor explained that he was saying thanks for an education that changed his life.

“It is a direct way of saying to people I appreciate what you did,” said Howard Gage, a mathematics professor who last June was sent on a tour of Britain. “The fact he is being anonymous means he is not in it for recognition.”

Gage, a former Whitworth student himself, was accompanied on the trip by another gift recipient, John Carlson, 87, who was once Gage’s math teacher.

Carlson also visited Sweden, and five months later, was sent to Hawaii.

So far, 14 men and three women, whose ages range from 50 to 87, have been awarded vacation trips. Early recipients were members of the science department; all are veteran teachers at Whitworth, where the full-time faculty numbers about 90.

Spike Grosvenor, an art teacher, received a three-week tour of England’s stained-glass churches. “It was a phenomenal experience,” he said, “and has had a real impact on my classes. It recharged my batteries.”

Grosvenor said that the mystery donor’s knowledge suggests access to a campus adviser or records. “He gets detailed information. He knew what I was teaching, what my specialty was. He knew I had never been to Europe and when I’d had my last sabbatical.”

The trip was followed by gifts of Cajun yams, a smoked ham and a coffee maker. But the biggest surprise came Dec. 23, when Grosvenor’s oldest son showed up for a Christmas visit.

Dennis Grosvenor, a waiter struggling to break into the music business in Los Angeles, had not been able to afford to come home. The donor knew this, and also knew how to contact him by phone at his girlfriend’s apartment.

Many Whitworth teachers could not afford to travel any other way. Grosvenor, for example, said he could earn $5,000 to $6,000 more than his salary at Whitworth by teaching at a local high school.

He is not surprised, though, that someone believes the college changed them profoundly. “Whitworth has historically made a big difference in people’s lives,” he said.

The college, which is celebrating its centennial year, requires undergraduates not living at home to reside on campus their first two years, and the student-faculty relationship is often close.

“We make a point of knowing our students,” said Nicolin Gray, a biology teacher who retired in 1980 and who was sent with her husband, Alfred, to New Zealand. The Mystery Man called her to explain he had been one of her students, but she was unable to guess his identity.

“It was a wonderful trip,” she said. “We could probably never have done it on our own.”

“It is unusual here to have a rich donor,” John Carter, the college’s spokesman, said. “For the most part, Whitworth alumni go into service professions. We have a lot of ministers, missionaries, nurses or public health doctors.”

“The experience has changed me,” said Patricia McDonald, a psychology teacher who got a trip to Hawaii. “I look for ways now that I can express my own generosity.”

Theories about the Mystery Man abound. Because the travel agent works in Bremerton, many suspect that the donor lives in the Puget Sound area. Bocksch, however, suspects that he is a former student living in Michigan who recently contributed $22,500 to the school’s chemistry department.

Most teachers at Whitworth are not anxious to solve the puzzle.

“The fun of it is to leave it the way it is,” Gage said. “I have no intention of finding out. It would destroy the mystery of the whole thing.”