Thursday, Grey's Anatomy airs what looks like the most intense episode of its sixth season so far. Entitled "I Saw What I Saw," the episode begins with a burn victim unexpectedly dying in the ER, leaving the Chief scrambling to figure out what happened.

Who's responsible? Who will be assigned the blame?

That we'll have to wait and see, but it's a foregone conclusion that the Seattle Grace-Mercy West rivalry will be ramped up to new levels as the hunt for answers ensues.

Below are episode stills from Thursday's episode of Grey's Anatomy. Click to enlarge ...

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