At age forty-nine, Eileen Flanagan had an aching feeling that she wasn't living up to her potential--or her youthful ideals. A former Peace Corps volunteer who'd once loved the simplicity of living in a mud hut in Botswana, she now had too many e-mails in her inbox and a basement full of stuff she didn't need. Increasingly worried about her children's future on a warming planet, she felt unable to make a difference--until she joined a band of singing...