hjbau wrote: Maybe Mary was taken and didn’t flee.
You’re probably onto something. I think Mary Margaret used the key to escape the jail cell, but that she was then taken. The promo for ep. 17 reveals that not only is Emma kidnapped by the Mad Hatter, but we also see that Mary Margaret is all tied up. It appears as if Mary Margaret is also kidnapped, either by the Mad Hatter or Regina.
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"That’s how you know you’ve really got a home. When you leave it, there’s this feeling that you can’t shake. You just miss it." Neal Cassidy