PROVO, UTAH -- Returning to his upscale Salt Lake City home after an evening get-together with Mormon friends, Mark Hofmann chatted with his wife, Doralee, until she went to bed about 11:30. Then he descended to his basement workroom and began assembling the supplies he had bought 10 days earlier: two lengths of threaded, one-inch pipe; two end caps; nails; and two cans of Hercules Bullseye gunpowder.

About 3 a.m., Hofmann got into his gold Toyota van to deliver the first of his two homemade pipe bombs to the doorstep of businessman W. Gary Sheets. In the darkness, he unhooked the tiny wires from a safety device and connected them to the mercury switch that, a few hours later, would blow up Sheets' wife, Kathleen, who picked up the package.

Hofmann was home by 3:30 a.m., when his sleepy wife, accustomed to her husband's nocturnal restiveness, called down from upstairs to ask him to tend their small daughter, who had awakened in the night. He stayed with the child until she fell asleep. It was Oct. 15, 1985.

At 6:30 a.m., Hofmann got back into the van and delivered the second bomb to the office of Steven Christensen, a former partner of Sheets and a Mormon bishop interested in the historic documents of his faith. Eighteen months earlier, Hofmann had sold Christensen the notorious "white salamander" letter, which linked the church's founder to the practice of folk magic.

The letter caused much disquiet at the time among Mormons and Mormon scholars. Christensen submitted it to church and other experts, who verified its authenticity, then donated it to the church.

Last week, almost two years after the murders of Kathleen Sheets and Christensen, more than 1,400 people -- three times the anticipated number -- attended a 13-hour symposium at Brigham Young University to consider Hofmann's short, dazzling career as a con man and forger of Mormon and secular historical documents and his impact on the faith he secretly abandoned in adolescence.

"The enormous damage done by Hofmann will take a long time to assess," said forensic handwriting expert Charles Hamilton, who had been fooled by some of Hofmann's work. "He will be out of prison, and at it again before we get around to finding out the real expense of his disruption of scholarship." Hofmann is serving five years to life as a result of a plea bargain, and the sentencing judge recommended that he never be released.

Of the 424 documents and memorabilia Hofmann is known to have sold to Mormon institutions and individuals, 107 are known to be forgeries, 60 are suspect and others have not been examined. "His deceit," BYU President Jeffrey R. Holland told the symposium, "has certainly not rocked the foundations of the church . . . but it has rocked the faith of some uncertain, and often very young, hearts and minds."

Most of his forgeries may not have involved the church, however. "From Beethoven to Daniel Boone, from Betsy Ross to George Washington -- only 20 to 30 percent of his output was Mormon," Mormon author Allen Roberts said. "His undetected forgeries will continue to have a selected impact for generations."

In early 1985, for example, Hofmann tried to negotiate $1.5 million deal with the Library of Congress for a document he claimed to have found in New York's Argosy bookstore -- the Oath of a Freeman, dating to the Massachusetts Bay Colony and thought by some to be a model for the Declaration of Independence.

His machinations came apart when he was critically injured the day after the murders by a third bomb. Police discovered that all three bombs had been built of parts purchased at a Radio Shack by "Mike Hansen." In Hofmann's workshop, they found a piece of paper bearing the name Mike Hansen and the number of a Denver engraver who turned out to have negatives of printing plates made for "Hansen" the previous year.

When police confronted Hofmann in his hospital room with this and other evidence, the alarms on his life-support monitor sounded, and nurses shooed them out. They had a suspect, but they had no motive.

"Why would this meek-looking, scholarly, respectable, almost a wimp of a man commit this horrible crime?" deputy Salt Lake County attorney Robert L. Stott asked rhetorically as he reconstructed the crime last week.

Hofmann was a Mormon luminary, in the headlines regularly with his amazing and spectacular finds relating to the church's early history. Six months before the bombings, he promised to tithe to the church another stunning find, the letters of a 19th century Mormon named McLellan. McLellan had left the church after a falling out with its founder, and his papers were expected to be highly critical of the church.

The church loaned Hofmann $165,000 to acquire the collection. But Hofmann already had received a $150,000 advance for the same papers from an antiquities dealer.

Under pressure to produce the collection for both buyers and repay the church loan, he told church officials that the failure of his negotiations with the Library of Congress for the Oath of a Freeman would force him to sell the McLellan papers instead. The church found a wealthy Mormon buyer, and Hofmann was to turn over the documents Oct. 13, 1985, at a meeting arranged by Christensen.

But Hofmann had no McLellan collection, had spent the money and never appeared for the meeting. He later confessed to killing Christensen to avoid being found out and planting the bomb for Sheets to cast suspicion on disgruntled investors in a troubled business venture in which the two victims had been partners.

Last January, Hofmann pleaded guilty to two counts of second-degree murder and two counts of fraud involving documents. Last month, the county attorney's office released a 600-page transcript of investigators' interviews in which Hofmann described his deception of the church in a career that spanned seven years.

How he did it and why -- his confessions describe his contempt for the church after his faith failed him -- have been easier questions for the church to deal with than the question of how much damage he did. Mormons were particularly vulnerable, Roberts said last week, because the church "ties its validation to the truthfulness of historical events. If those events did not occur, {Mormons} would know the church cannot be true."

The Mormon Church -- the Church of Jesus Christ of Latter-day Saints -- was founded by Joseph Smith Jr., who told his followers that an angel led him to golden tablets containing the church's tenets.

Hofmann first approached Mormon officials with what deputy county attorney Stott described as "faith-enhancing" documents that tended to fill in the blanks in church history. One of his forgeries was a letter from Smith's mother, corroborating his accounts of angelic visitations.

Gradually, however, his documents became more controversial. The salamander letter purportedly was written by a friend of Smith and portrays him as deeply involved in the occult, an image Mormons hardly wished to promote of their founding prophet.

For a time, Mormon officials withheld the letter and other documents that appeared to undermine the official version of church history.

Elder Dallin H. Oaks, a member of the Council of the Twelve, a church ruling body, defended the church's lack of skepticism in dealing with Hofmann, himself a respected Mormon. ("Ministers of the Gospel function best in an atmosphere of trust and love," he said. "In that kind of atmosphere, they fail to detect a few deceivers they meet.") And he devoted half of an after-dinner speech to denouncing coverage of the scandal as "a media feeding frenzy."

Hofmann's forgeries, prosecutor Stott said, "were good. He did excellent work . . . . He didn't look like a con man." But Stott, a Mormon and a BYU law school graduate, said church historians had been too gullible and should have investigated Hofmann's stories about how he found his documents.

BYU professor and historian Ronald Baker responded to such criticism by tossing out his prepared address to the symposium and making an impassioned plea for understanding, praying that Hofmann's "duplicity . . . will not further befoul our community with unkindness."

"Anyone delving into the Mormon past will find what they want," BYU historian William G. Hardley said. "Their faith or lack of it will predetermine how they will mine the past and to what use they will put it . . . .

"It is imperative for any who write Mormon history to use the records of the past honestly and exercise . . . great caution when facing newly found records whose {origins} are in doubt."