Molly Parker has signed on for a sisterly role on Showtime.

The former Deadwood actress will recur on season six of Dexter as the sibling of Colin Hanks' Travis. The latter character, an expert in ancient artifacts, is rumored to be the main foe of our favorite blood expert this fall.

Parker has appeared on Human Target and Boardwalk Empire. No word yet regarding how many episodes she'll appear on.

[Photo: Pacific Coast News]

Matt Richenthal is the Editor in Chief of TV Fanatic. Follow him on Twitter and on Google+.