In Plain Sight Episode 4.12 A Womb with a View

Mary proves it takes one to know one when she visits a mafia-mistress-turned-witness named Grace Haddik, and discovers what both Marshall and Stan missed: Grace is pregnant. Very pregnant. Now that Grace's bun in the oven is out in the open, Mary and Marshall must do their best to keep mother and baby safe. Which in Mary's case means posing as Grace's life partner and holding her hand through the birthing process.

And as if witnessing the miracle of birth isn't enough to disturb Mary, she has a hunch that the new mom is up to something. And unfortunately it seems like it might involve her ex, a powerful Persian arms dealer and drug trafficker. When Mary and Marshall begin to put the pieces of Grace's deception together, they start to wonder if this conniving new mother might have been playing them all from the start.

As Brandi's rehearsal dinner brings a surprise visitor to town and Mary continues to make plans for her own baby, Mary can't help but find Grace's case hitting close to home-and bringing out her latent maternal instincts. Turns out they do exist; they're just very, very deeply buried.