New faces like Sadie (Melissa George) and old ones like Denny (Jeffrey Dean Morgan) are shaking things up at Seattle Grace, and tonight's episode looks like no exception.

In this week's episode, "In the Midnight Hour," Lexie and her intern cohorts get in way over their heads with their surgical experimenting. Can Mer and Cristina save the day?

Also, Izzie is very excited about somebody, as one of the videos we've posted previewing the episode makes quite clear. Check out our photo gallery for more sneak peeks.

As always, you can discuss it before, during and after the show in our

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