The Flash star Grant Gustin showed off his pipes on seven episodes of Glee, but now his current co-stars are getting their time in the spotlight. In this video, Jesse L. Martin, Carlos Valdes, and Rick Cosnett sing an a capella version of "The Ballad of Serenity," the theme song from Joss Whedon's beloved TV series Firefly. Why? The trio is apparently working on a short film called The Letter Carrier and were trying to raise funds on Kickstarter when Whedon himself came in and donated enough to allow them to reach their goal, so they decided to sing this song as a way of saying thank you. It makes sense, considering the plot of their short film relies heavily on music:

A mother hides her family from slavery in the Blue Ridge Mountains. The children have grown up with a tale of a man known as The Letter Carrier. As the legend goes, he roams the mountains looking for children to sell as slaves. Painted against this historical backdrop, it is a raw, mysterious, and interpretive fable. Told through a cappella song, using original folk music, spirituals and a score using only natural sounds.

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