Sept. 7, 2010— -- The husband of missing Utah mother Susan Powell maintains his wife simply walked away from her family, even as his own sister said she's "quite convinced" he was involved in her disappearance.
"Has he kidnapped her, holding her somewhere? Has he killed her?" Josh Powell's sister, Jennifer Graves, asked. "Who knows?"
Eight months after Susan Powell disappeared from the couple's West Valley City home, her husband -- who provided a bizarre alibi about a winter midnight camping trip with his toddlers -- continues to fend off accusations from her family and his own.
Kirk Graves, Jennifer's husband and Josh Powell's brother-in-law, said his behavior after Susan Powell disappeared was telling.
"Josh's reaction was, don't talk to anybody, be of no help -- not even family. Just get out," he said.
Josh Powell has not been charged in the case and police have yet to make any arrests.
The family who supports him -- namely his father Steven -- maintains that the negative comments toward him are religiously motivated, that the Mormon church that Susan Powell was so deeply involved with has organized to attack him.
In a statement to ABC News, Steven Powell argued that his son has done everything to help police find the mother of his children even as Josh Powell's sister and brother-in-law claim he's done little but push her family and the police away.
"Clearly, we think Susan decided to leave," Steven Powell wrote. "This has little to do with Josh because their marriage was basically normal. There is no evidence to the contrary."
"Although (Susan's parents) would like the public to believe otherwise ... most of the time it was a happy and stable relationship," Steven Powell continued. "However, Susan had an occasional tendency to lose control."
It's a characterization of the 28-year-old mother that her friends say is completely untrue.
"They would get in fights and talk about divorce and she would say. 'I'm going to take the kids,'" Susan Powell's close friend Kiirsi Hellewell said. "And he would say, "No. Over my dead body.'"
Graves said her brother was controlling and watched over his wife carefully.
"He controlled the money, the car," she said. "He wouldn't let her go to activities and things without his approval."
Susan Powell was last seen Dec. 6. She went to bed early, but Josh Powell said he bundled up the boys, then 4 and 3, on the cold winter night and took them camping around midnight to a campsite about two hours away.
When they returned, Susan Powell was gone. Police found her purse and keys in the house and, strangely, two fans drying a wet spot on the living room floor.
Susan Powell's Father Warns: 'We Are Not Going to Quit'
Powell, who was still out with the boys when a daycare provider realized the family was nowhere to be found, was reached on his cell phone and told to come home.
He was questioned by police, but that information, along with other forensic evidence, have been sealed. Powell has told local media outlets of his middle-of-the-night trip that "we were just going to do s'mores."
Graves said it's hard to think that her own brother may have kidnapped or killed his wife.
"But you have to remember that she was my sister and she's gone. She's my friend. Where is she?" Graves said. "I haven't seen her for eight months."
Susan Powell's father said he's equally convinced his daughter's husband is guilty.
"It's our understanding from hearing it from three sources that Josh was not going to give up the children. That he would cause her physical bodily harm," Chuck Cox said. "She feared for her physical safety."
Josh Powell is now living 900 miles away from West Valley City in Puyallup, Wash., with his father.
"I think whoever is responsible needs to realize that we are not going to quit. And it's not going to stop until the truth is known," Cox said. "And anybody who doesn't believe that is not being real. So come forward."