This Sunday, April 12: A big choice for a little kid, a modeling scam, and an online dating shocker

NBC's Hoda Kotb has the story of a 13-year-old boy named Sam who is funny and smart and kind of a goofball. So when he starting limping and falling down for no apparent reason, his parents thought he might just be fooling around. They were wrong. His body had begun to change in terrible ways his family couldn't understand. His doctor came up with a risky plan that just might save him, but Sam would have to agree to it. It would be a terrifying decision. But if his body was betraying him, maybe his courage would see him through.

Also: For many girls, it's the ultimate fantasy: to be discovered, and make it big as a model or actress. And, wouldn't you know, there are people standing by to help make that dream come true, offering everything from classes to meetings with casting agents. And lots of loving parents are willing to pay thousands to help their daughters reach for the stars.... But do they always get their money's worth? What we found out isn't pretty. Correspondent Chris Hansen brings us a Dateline hidden camera investigation.

Plus: Two beautiful, vivacious women meet a man online who seemed destined to change their lives. He sure did that. To one he promised opportunity and to the other, he offered love and money. But it turns out he was making lots of offers to lots of women - and walking away with their money. When you see who he was, and how he did it, you may be as shocked as the victims themselves. Dennis Murphy has the story of the Mysterious Music Man.