The 52-year-old joined the show in season four as Katherine Mayfair, a housewife who may have been responsible for her ex-husband's death.
Delany told Entertainment Tonight: "I'm coming back, yes. My whole mystery story will be wrapped up and everything will be revealed, and it's rather dramatic."
Delany's credits include TV shows Kidnapped and China Beach, as well as film roles in Tombstone and Exit to Eden.
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