At times, he's indistinguishable from any other 12-year-old with a crewcut. At times, his words get tangled and his body betrays him -- arms and wrists flapping as if convulsed by a sudden surge of electricity.
Some autistics are self-abusive, and many are tactile sensitive in strange ways. A caress can be repulsive, a rib-rattling bear hug soothing.
Temple Grandin, a 56-year-old professor at Colorado State University who's achieved cult status by writing frequently about her autism, built a "Hug Machine" that resembles a giant book jacket made of plywood. She regularly climbs inside and presses herself like a leaf.
Mason prefers conventional hugs and kisses. Lots of them. Still, he's the ultimate creature of habit, a telltale sign of autism that his tutor thinks is one reason they hit it off so well.
"I understand a lot of his quirks, I guess you could call them," Allyson says. "I'm very structured, and he craves structure."
Lunch must be at noon, dinner promptly at 6 o'clock. Friday afternoon is the weekly pilgrimage to Blockbuster Video. Sunday wouldn't be Sunday (can't be Sunday) without the New York Times movie section.
He won't take refills on drinks, hates the feel of sand on his hands, gets upset if an Orioles game goes beyond nine innings, and usually refers to himself in the third person. "Mason's brain's on fire!" is his way of announcing a headache.
Surprises are not welcome. Ever. The recent emergence of body hair was a crisis that required B.J.'s repeated assurances that everything was OK: Dad's got fuzzy legs, too.
These quirks could become obstacles to social acceptance as Mason gets older. He sees a psychologist and occupational and speech therapists, but Allyson makes a point of working on his life skills. They take field trips to the beach, Boston and Broadway shows, sometimes accompanied by her fiancee.
She makes him order and pay for restaurant meals. She tells him it's really not polite to turn to someone in an elevator, as he did last summer, and say, "Excuse me, sir, you smell."
Family and friends keep reminding Mason that his prodigious memory is a gift. He realizes he's different -- and is beginning to understand others know, too.
Last year Allyson took him to a party at her sister's apartment. Somebody in the room whispered that Mason was a "Rain Man." He heard.
"I'm not Rain Man!" he stammered. "I'm Mason! I'm Mason!"
Polly Winde was raised in Ellicott City; William James Surhoff in Rye, N.Y. Both now 39, they started dating during their freshman year at the University of North Carolina.
She was an elite collegiate swimmer who placed fourth at the 1984 Olympic trials and later was inducted into the Maryland Swimming Hall of Fame. He was the top pick in the 1985 amateur baseball draft, chosen by the Milwaukee Brewers ahead of Rafael Palmeiro and some string-bean outfielder named Barry Bonds.
The Surhoffs have complementary, cog-and-gear personalities. Polly is extroverted, the family's unofficial spokesperson. B.J. tends to wear his game face 24 hours a day -- a gracious, low-key man more at ease on the fringes of a cocktail party, if not behind the drapes. He and his youngest son take their time sizing up strangers.
"B.J.'s a private guy," says close friend Cal Ripken. "It does take awhile to get into his inner circle. You don't always know what Mason's thinking, either."
For a long time, the Surhoffs never knew what Mason was thinking. Austin's birth in 1990 had been blessedly uneventful. His brother's was too, but, as is common with autism, something went awry at about 18 months. Those tantrums kicked in. Mason stopped vocalizing and started to withdraw.
Polly's stepfather rang a dinner bell near his ear one day to check the reflex response: nothing.
The Surhoffs, then living in suburban Milwaukee, had Mason's hearing and blood tested. Polly took him for a CAT scan, triggering an epic tornado. She got in the car afterward and just kept driving. Something about being in motion soothed her hysterical son. She drove all the way to Chicago and back.
In early May 1994, B.J. met with a pediatric neurologist who delivered the official diagnosis. No small talk. Just a shotgun blast of bad news.
"It was kind of, 'This is what your son has. Now go deal with it,' " B.J. recalls.
Stunned, he went home and told his wife, who had only recently learned she was pregnant with Kendall. Those days are a blur to Polly. B.J. felt helpless.
"You're scared to death," he says. "There's not a pill, a surgery, a treatment. It's a lifelong neurological disease. All that goes through your head. Was it me? Was it us? Did we do something wrong?"
Luckily, they had the financial resources to pay for whatever professional help might be needed. But Polly thinks their sports background proved just as valuable. Athletes are accustomed to dealing with adversity, to not accepting limitations.
Polly devoured books about autism. She attended seminars. The quest for hope nearly consumed her.