Based on an initial incident report obtained by CNN, we know the women -- Amanda Berry, 27; Georgina "Gina" DeJesus, 23; and Michelle Knight, 32 -- say they were beaten and sexually abused. One says she suffered at least five miscarriages induced by starvation and beating. And we know they only rarely, and briefly, left the home on Seymour Avenue that had become their prison.
But some questions remain unanswered in this case. Here's a look at a few of them:
Did anyone know? And if not, how could that be?
It seems implausible -- three women, and later a child, held captive for close to a decade within a 1,400-square-foot home in a densely populated urban neighborhood without anyone else knowing.
Wouldn't his brothers or other relatives, his children -- somebody -- have noticed something strange going on?
At first, authorities seemed to think so: they arrested Castro and his two brothers on Monday, saying initially that the brothers were linked to the investigation. On Tuesday, however, they said that didn't seem to be the case.
One explanation may be Castro's penchant for obsessive privacy around his home, according to the father of his late common-law wife.
Ishmael Figueroa once shared a home with his daughter, Grimilda Figueroa, and Castro. Figueroa lived downstairs, the couple lived upstairs. Castro, he says, would never let anyone visit the second floor.
And when Castro and Grimilda Figueroa moved to the house on Seymour Avenue -- where the women were later discovered -- Castro wouldn't even let family members through the front door.
"Ariel kept everybody at a distance," said Cleveland Deputy Police Chief Ed Tomba.
Could Castro be charged with murder?
It's an intriguing question. Ohio is one of 38 states with a fetal homicide law, according to the National Conference of State Legislatures.
Authorities have searched Castro's home and found no evidence of human remains. But in her initial interview Monday with police, Knight told investigators that she had suffered at least five miscarriages, according to the incident report obtained by CNN.
Castro would starve and punch her in the stomach to induce miscarriage, Knight said, according to the document.
Authorities haven't publicly discussed such an idea, but CNN affiliate WOIO -- citing multiple law enforcement sources -- said authorities are investigating the possibility of murder charges against Castro.
Will anyone get the reward?
Berry's and DeJesus' disappearances were frequently in the news, and a $25,000 reward was on offer in the case.
In the immediate aftermath of Berry's daring escape, speculation centered on whether Charles Ramsey, one of two neighbors who came to her aid, deserved the reward. Ramsey himself suggested the money should go to the women.
Authorities haven't concluded who, if anyone, should get the money, but are discussing it, Tomba said.
"That is going to be up to the entities that put up that reward money and what their protocol is, but Mr. Ramsey does deserve something. A lot of credit and he is the true key to this case," Tomba said.