Cahill will play Big Jim's (Dean Norris) brother-in-law Sam, a former EMT who has a connection to Julia (Rachelle Lefevre). Meanwhile, English actress Crome will play Rebecca, a former Army brat who is now a teacher.
But don't worry about the cast getting too overcrowded. It was announced at Television Critics Association winter press tour last month that two characters will meet their demise on Under the Dome's upcoming second season.
Under the Dome returns Monday, June 30 on CBS.
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