All the warning signs were there for Glen and Helen Morris: the tenant who wanted to spend $25,000 to redecorate a rented house, the complaints about the strange men with briefcases arriving after dark and the suggestions from neighbors that "we call the FBI."

The Morrises asked some of the right questions: Why, for example, did their tenant want to soundproof a room in their Georgetown townhouse? "I do a lot of recording," they recall him saying.

But it was not until this week when they saw pictures of a Northwest Washington house used in the FBI's Operation ABSCAM, for Arab scam, that the pieces fell into place, and they realized that their house, too, had been used for some sort of undercover operation.

The large townhouse at 1536 32nd St. NW was not part of the same operation that has allegedly implicated eight members of Congress in potential bribery charges.

It was part of another FBI undercover operation, which is still continuing in another city, according to sources.

The way the bureau obtained the Morrises' townhouse is almost identical in every detail to the way it obtained a house at 4407 W St. NW for its ABSCAM operation.

The Morrises were suspicious of their tenant, whom the FBI has asked not be identified, from the start. He claimed to have made a fortune in the Mideast working for some sheik. In Washington, there are stranger stories, and the Morrises believed this one -- for a while.

The tenant wanted to redecorate the house almost immediately. Everything would be repainted, he said. There'd be new carpets, new drapes, new light fixtures, an elaborate new burglar alarm system, and the soundproof room in the basement.

The tenant, a soft-spoken man in his 40s who claimed to be president of Metropolitan Electric Co., said he would pay for all the redecorating which he estimated would cost in excess of $25,000.

Helen Morris, an interior decorator, was suspicious, though, and worried about what the tenant would do to the house.

"Let me take you to see another house we've already done," her son, Glen Jr., recalls the tenant saying.

The tenant took them to a large, brick colonial on W Street. That was in October 1978, shortly after the Morrises had signed a two year, $1,285-a-month lease for their house.

The W Street house was leased by a man claiming to be the secretary-treasurer of the Arlington-based Olympic Construction Corp. The Morrises' tenant said he was president of Metropolitan Electric Co., but the insurance policy written on the townhouses was made out to Olympic.

When Olympic was called yesterday and a secretary was asked if the Morrises' tenant was employed by the company, she first said, "Wait a minute. I'll check." After a moment, she returned to the telephone and said "No comment."

The Morris house was occupied until last August. The FBI completely redecorated it and installed an elaborate security system. Hallways and the basement were carpeted, and orange drapes hung in the living room. Silver chandeliers were hung in the dining room, and track lights in the hallways. The Morrises believe that the lighting changes were made to hide bugging devices.

Helen Morris was upset. "She said she could have done a better job than the FBI's decorator. He was a crummy decorator," her husband said yesterday.

Neighbors complained about vans with New York license plates parked in front of the house. They also reported that men entered it at odd hours.

"The lady next door thought it was the Mafia because of all the night activities," Morris said. "She kept waiting for us to call the FBI. Myself, I thought it was the CIA."

The tenant notified the Morrises that he wanted to move out last summer. "He said his business was going broke and his wife was leaving him," said Glen Morris Jr. "We felt real sorry for him."