Theresa, believing that without Ethan's help she'd never regain custody of her son, resorted to stealing Ethan and Gwen's embryo and having herself implanted with it, intending to exchange their child for hers once it was born. But when she believed she had miscarried the baby, she sank to still more desperate measures; after slipping a dangerous date rape drug into Ethan's drink, she dressed up as Gwen, climbed into his bed and had sex with him. Though Ethan knew it was her and denied it until after Jane was born.