The mother of five children who allegedly were sexually abused by Adderli Jose Cruz-Rosario poses for a portrait in Silver Spring. (Matt McClain/The Washington Post)

Montgomery County detectives investigating allegations of child abuse have painted a picture of a monster. Adderli Cruz-Rosario, they said, sexually abused five young children and threw one of them, a toddler, across a bedroom into a wall — a child later shown to have nine healing rib fractures inside her 18-pound body.

But there are other pictures of Cruz-Rosario. They are stored as videos and photographs in the smartphone of the children’s mother. They show the 20-year-old suspect laughing and playing with her smiling kids.

“They look so happy,” the 27-year-old mom said from her apartment in Silver Spring recently, looking at her phone during one of several extended interviews about the case.

She wants to know the truth about Cruz-Rosario, who lived in her apartment and decorated the kids’ rooms with fresh paint — adding glitter for the girls and the number 95 for the boys, a reference to the animated movie “Cars.” He took care of the children for long stretches while she worked as an office manager at an accounting firm.

“Every minute, every day, I’m always thinking about what happened,” she said. “If it did happen, why?”

The Washington Post is not naming the woman to protect the identity of her children. She has doubts about the case, mostly because her children never told her of abuse. Cruz-Rosario has yet to give his version of the events in court. He remains locked up on $1 million bond.

But if the accusations against Cruz-Rosario are true, the woman’s experience — along with her questions and replaying what she might have missed — offer insight into what experts say is an all-too-common phenomenon.

Sheri Rettew, the board chairman of a group called Stop the Silence: Stop Child Sexual Abuse, said abusers can groom a child not only to keep the abuse a secret but to smile later as if nothing is wrong. “They’re really good at this,” she said. “This is what they’re best at.”

In the Silver Spring case, the mother’s worries are compounded by the fact that her children have been taken from her — sent to foster homes and, in the case of her oldest three, to their biological father. The mother sees her kids once a week, at a county-supervised house designed for such visits.

“Mommy! Mommy!” two of them could be heard greeting her as she approached.

She is not allowed to speak with them about the case. She wants to ask them what happened, tell them they did nothing wrong, take them home.

“If he did this, I’m their mother — I need to be the one to talk with them,” she said.

By her own frank admission, the woman has had her share of struggles. She became a mother as a teen and has given birth to eight children; seven of the births were Caesarian sections. Her family has been on food stamps. And for a brief period last year, she and her kids were homeless, and the county put them up at a hotel.

But the woman has been employed, earning nearly $1,000 a week during tax season. She has tried to push her kids to succeed — to get a college degree, to find a spouse who will stay forever. “To me, each one is a blessing,” she said.

In 2011, she met Cruz-Rosario through a family member. A year later, he moved in and was immediately attentive to the children in ways that she said she’d never seen from their biological fathers. He cooked. He cleaned up after the kids. He combed their hair, taught them how to walk, took them to a community swimming pool. “It was different,” she said.

Cruz-Rosario was extremely playful with the kids, on occasion tickling them and pretending he was going to bite. “I told him I didn’t like that,” she recalled. A daughter told police that she had alerted her mom about the biting, but she didn’t take it seriously, according to court records.

One day late last year, the woman and Cruz-Rosario noticed that her youngest daughter had a problem with her leg. “Look at how she’s limping,” she said Cruz-Rosario told her. “Let’s take her to the hospital.”

The child had a fractured tibia, and her leg was placed in a cast. Cruz-Rosario said he didn’t know what happened. To the mother’s thinking, he was the one leading the effort to get medical care. She attributed the injury to a fall or the girl’s many siblings playing around her in their tight, three-bedroom apartment.

On April 10, the mother arrived home from work to see bruises on the same girl’s cheek. She asked Cruz-Rosario, who told her to ask the other children. One of them said the girl had fallen from a bed. Two days later, the bruises had become more pronounced and the girl was running a fever. Her mother took her to their pediatrician.

The doctor thought the bruises resembled bite marks. She called county social workers, and the system swung into action.

The child was taken the Children’s National Medical Center for tests. Among the findings: the healing rib fractures and possible damage to her pancreas and brain. “The overall picture is indicative of a battered child,” concluded one physician, according to police affidavits in the case. A separate examination uncovered evidence of sexual abuse, according to affidavits.

Detectives questioned three of the girl’s siblings. The investigators used open-ended questions, letting the children guide the discussion, said Capt. Bob Carter, director of the family crimes unit at the Montgomery County Police Department. The 8-year-old girl said Cruz-Rosario had hit her in the face, legs, chest and shoulders, according to the investigators. The 10-year-old boy said Cruz-Rosario had “constantly” hit his siblings with his hands and belts. This boy told investigators that he saw Cruz-Rosario pin the toddler under fitness weights to try to get her to sleep and that a short time later the boy freed her, according to police affidavits. Another child, an 11-year-old girl, told detectives: Cruz-Rosario “likes to bite us.”

In June, the detectives spoke with the children again, according to arrest records. The kids began to say that Cruz-Rosario had also abused them sexually. Detectives concluded that five children were sexually abused.

The accusations are spelled out in the affidavits, which the mother has read. With each detail, she has another round of competing thoughts: If it’s true, Cruz-Rosario should pay. But how could it be true if the children never told her?

“I go back and forth,” she said.

She visits Cruz-Rosario at the jail and speaks with him on the phone. “It’s not anything like they’re saying. It’s all lies,” she recalls him saying. “Ask the kids.”

The detectives have told her to stop talking with Cruz-Rosario, she said, but she is looking for answers. “If I can get it out of him, I will,” she said. “That’s why I keep talking to him.”

Jennifer Jenkins contributed to this report.