The fourth and final season of The Unit started on September 28, 2008, and concluded on May 10, 2009. The season included 22 episodes and introduced Bridget Sullivan (Nicole Steinwedell) and Sam McBride (Wes Chatham), new members to the unit and the team. It was announced on May 19, 2009, that CBS declined to renew the series for a fifth season, along with Without a Trace. For the 2008-09 U.S. television season, the fourth season of The Unit ranked #43 with an average of 10 million viewers.