(CNN) -- Exactly one week ago was the last time anyone saw little Maleah Davis.
Darion Vence, the 4-year-old's stepfather, initially told police that he was driving to a Houston airport with Maleah and her 1-year-old brother on May 3 when he was attacked and the three were abducted by three Hispanic men. The abductors eventually dumped Vence and the boy alongside a road, he said, but Maleah was gone.
Police say the stepfather's account of what happened last Friday night has changed several times, and Maleah's mother, Brittany Bowens, says she doesn't believe his story.
Police and Bowens said they have been trying to contact Vence now for several days, but they have not heard from him.
Here's what we know about the case:
Stepfather says he was attacked and abducted
Vence told police he and the two children were driving to George Bush Intercontinental Airport in north Houston to pick up Maleah's mother, who had been in Massachusetts.
Vence says he heard a "popping noise." Thinking it was a tire, he stopped to check. A blue pickup truck then pulled up behind his car and two Hispanic men got out.
One of the men said, "Maleah looks very nice, looks very sweet," Vence told the police.
That's when the other man hit Vence in the head, and Vence blacked out.
Going in and out of consciousness, Vence said that at some point, he was aware of being in the back of a pickup with both children and three Hispanic men.
When the stepfather comes to, Maleah is gone
Vence says he didn't fully regain consciousness until the next day. At about 6 p.m. Saturday, he awoke to find himself and the boy on Highway 6 in Sugar Land, southwest of Houston. Maleah was gone.
Vence then walked to a nearby hospital and was treated. An off-duty police officer noticed that Vence had fresh wounds, CNN affiliate KTRK reported .
Police issued an Amber Alert for Maleah on Sunday.
"I realize there's a lot of blanks in the story," Sgt. Mark Holbrook of the Houston Police Department's Homicide Division told reporters. Police hoped the public could help them "fill in the blanks" in the narrative provided to them by Vence.
Maleah's mother pleads for her return
In the meantime, Maleah's mother, Brittany Bowens, had gotten a ride home from the airport from another relative after Vence didn't show up.
Sobbing, Bowens pleaded for help in an interview with CNN affiliate KTRK earlier this week, saying she is "terrified" for her daughter.
"I can't concentrate, I can't focus," Bowens said. "It's so overwhelming for me. It doesn't seem real."
Police: Story doesn't add up
Vence's account of what happened "did not add up," Sugar Land police spokesman Doug Adolph told CNN Wednesday.
Also, "the substantive details of what he described to us changed" over the days since he first recounted the events to police, Adolph said, declining to give details.
Bowens told CNN on Friday that she doesn't believe Vence's story and thinks he is partially responsible for her child's disappearance, because "the way he's going about things is suspicious."
"He hasn't called me, I haven't heard from him since Monday, I don't know what's going on," Bowens told CNN's Nick Valencia in an exclusive phone interview. "If you're innocent, why can't you say it yourself? Why aren't you defending yourself?"
CNN has reached out to Vence several times, but hasn't been able to talk to him.
Stepfather's car is found
The car Vence was driving, a silver Nissan Altima, was found Thursday morning in the parking lot of a shopping mall in Missouri City, Texas, about 4 or 5 miles from where Vence said he regained consciousness.
The car's condition appeared normal, with no visible blood or any obvious signs that something may have happened inside, said Ken Fregia, a homicide detective with the Houston Police Department.
Police are running forensic tests on the car as well as looking for surveillance video from the shopping mall and a nearby Walmart.
Allegations of abuse
Maleah and her two brothers were taken from their home and placed with a relative after allegations of abuse last year, the Texas Department of Family and Protective Services told CNN.
Bowens said the children had not been abused, and that Maleah's head injury, which had led to the allegations, was only discovered after a number of hospital visits. Maleah was first treated for a strange lethargy, and a week later, she fell and cut her head while sitting at a table. The doctors discharged Maleah without performing a CT scan, Bowens said.
Maleah had a seizure five days later, and that's when doctors discovered bleeding on the left side of her brain and operated on her, Bowens said.
Child Protective Services showed up a few days later, Bowens said.
"They didn't find anything because we're not those kinds of people," she said.
But authorities soon placed Maleah and her two brothers with relatives, where they stayed until a judge ordered them to be returned home in February.
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