(KRON) -- A woman was having a romantic affair with a Walnut Creek man when he allegedly murdered his wife and mother-in-law, according to investigators.

The accused mistress, 45-year-old Yan Wang of Oakland, will make her first court appearance Tuesday afternoon. Prosecutors charged her with helping the suspected killer cover up a double homicide on September 18 in Walnut Creek.

Her romantic partner, 43-year-old Howard Wang, is charged with murdering his wife, Linlin Guo, and his elderly mother-in-law, Beimin Cheng, prosecutors said. "Howard Wang was married to Linlin Guo but was in a romantic relationship with Yan Wang at the time of the murders," the Contra Costa County District Attorney's Office wrote.

Yan Wang and Howard Wang are not related, prosecutors clarified.

Police said bot

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