This summer at least four young people attending music events in New York, Boston and Seattle died, apparently after taking the party drug "molly."
Molly, or MDMA, is the chemical in ecstasy, the 1990s club drug.
It's very popular these days because it is perceived to be purer than ecstasy and it induces a feeling of euphoria and empathy towards others.
But because it's often sold in powder form, it can be adulterated with other substances and many users aren't aware of that.
Doctors who have studied molly say it speeds up metabolism and users who overdose at clubs and dance parties don't feel it at all until it's too late.
This segment aired on September 4, 2013.