After seven years as a Houston homicide detective, Johnny Bonds thought he had seen it all. Then, one July morning in 1979, he was called to a comfortable home in the city's southwest section. There, in the nursery, 14-month-old Kevin Wanstrath lay in his crib, snug in his blue terry-cloth pajamas, one dimpled hand clutching his teddy bear. He was dead—killed by a bullet fired into the back of his head from a range so close the gun's muzzle blast had singed his dark curls.

In the family den, Kevin's father, John, 35, an oceanographer, sat slumped in an armchair, shot twice in the back of the head. The baby's mother, Diana, 36, lay on the floor, her head resting on a book of nursery rhymes, shot once in the right temple. Though no gun was found at the scene, the medical examiner considered the case a murder-suicide—concluding that Diana had shot her husband and Kevin, then taken her own life.

But Johnny Bonds was not convinced. His own hunch was that the three had been executed by a hired killer. The sight of the murdered child continued to haunt him, and finding the gunman became his bitter obsession. "I didn't want to do anything but break that case," recalls Bonds, 34. "For two years, I was hardly ever home, and when I was, I would be on the telephone or just staring and thinking. I couldn't get over that baby."

Finally, last spring, Bonds' painstaking detective work, much of it on his own time, led to the convictions of four men. He had uncovered a gruesome web linking the Wanstrath murders with the death of Diana's 60-year-old mother, Gertrude Duff-Smith Zabolio. Mrs. Zabolio had been found dead in October 1975, with a pair of panty hose wrapped around her neck. Though her husband, Houston builder Dow Zabolio, and Diana had both doubted the finding, Mrs. Zabolio's death too had been classified as a suicide. She had left $90,000 to her daughter—and another $90,000 to an adopted son, Markham Duff-Smith.

Duff-Smith, ostensibly an insurance salesman, was actually a high-living speculator who soon squandered his inheritance on high-priced real estate, cars and the stock market. Three days after the Wanstrath killings, Bonds received a tip that Duff-Smith had arranged his mother's murder through a middleman identified only as a coin collector. Then Bonds discovered that a few months before the Wanstraths had died, Duff-Smith had sold John Wanstrath a $250,000 life insurance policy. As executor of Wanstrath's estate, he stood to inherit some $500,000 in the event that neither Diana nor Kevin survived. Bonds had found a motive for the killings but could prove nothing—not even after he tracked down the "coin collector," a big-talking entrepreneur named Walter Waldhauser.

The day after the medical examiner's formal murder-suicide ruling, Bonds remembers, "I got so many calls from crying women—friends of Diana's—that I could hardly stand it. They kept begging me not to stop working on the case." And Bonds didn't. For months he kept track of Duff-Smith's wheeling and dealing. Then, in the spring of 1980, Duff-Smith and Waldhauser made a critical error: They dumped their wives and moved together into Duff-Smith's expensive new house. The spurned wives commiserated and then talked with Bonds. Waldhauser's wife told Johnny that her husband had a friend in prison. The trail soon led to a paroled burglar, Allen Janecka, whose girlfriend, located in Georgia, turned over the gun used in the Wanstrath killings. Janecka was arrested, and confessed to killing the family, implicating Waldhauser as the go-between in the case. Waldhauser joined the chorus, naming Paul MacDonald, a former Houston bail bondsman, as a middleman in the Zabolio murder and fingering Duff-Smith as the man who put up some $20,000 to pay for the killings.

Meanwhile, Bonds' long investigation was leaving his private life in ruins. "When he'd finally come home, it was like he wasn't even here," says his schoolteacher wife, Carol, 34. "It got to where I couldn't stand to talk with him. It seemed like everything in our life was negative—like he was neglecting his own family for a dead one he didn't even know." The Bonds' two children, Aaron, now 10, and daughter Stacey, 12, were also troubled. "They said if it weren't for the police department," Carol recalls, "all this wouldn't have happened."

Bonds moved out of his house last January after he and Carol planned to divorce. Then, two months later, he went to Duff-Smith's house to arrest him. The suspect was in the bathroom shaving. "I told him he was under arrest," says Bonds. "He just blinked and didn't say anything. I loved it." Subsequently, MacDonald was sentenced to 16 years in prison and Waldhauser to 30. Allen Janecka, the hit man, received the death sentence. Duff-Smith, 34, the only defendant not to confess, was indicted for the murder of his mother, and Bonds took the witness stand at his trial. Recalls a friend of Diana Wanstrath's: "When the DA asked him why he pursued this case even after the medical examiner had ruled it a suicide, that big, macho guy just stopped. The tears streamed down his cheeks and he couldn't talk. Then he said, 'Because Diana was accused of killing that baby.' He cared so much."

By the time he was called on to testify, Johnny Bonds had returned to his family. On Easter Sunday, after Duff-Smith's arrest, he had joyfully called Carol at home. "He said, 'I woke up this morning and went outside,' " she remembers. "He told me, 'The sun was shining, the birds were singing and it was an entirely different world.' " A few days later Bonds moved back with her to stay. Commended by a grateful police department, he now recalls his ordeal with a sense of relief. "I knew I was right," he says, "and I felt I had to stand by what I thought. It caused a lot of suffering, but I think it was worth it."