Sherry Stringfield

ER alum Sherry Stringfield has joined the cast of Under the Dome for Season 2, TVGuide.com has learned.

Stringfield, who is best-known for playing Dr. Susan Lewis on the NBC medical drama, will play Pauline, a mysterious woman who may be connected to the origins of the dome. Other details about her character are being closely guarded, but you can connect the dots.

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"I'm thrilled after all these years to be working again with Sherry Stringfield," executive producer Neal Baer says. "We had a blast on ER together and I know Sherry will bring the same grace, spirit and intensity to her new, pivotal role onUnder the Dome."

Stringfield, who will be a recurring guest star in multiple episodes, joins previously announced Season 2 additions Eddie Cahill and Karla Crome. Her credits also include NYPD Blue, Guiding Light and CSI.

Under the Dome returns Monday, June 30 on CBS.

(Full disclosure: TVGuide.com is owned by CBS.)