How do you follow up a perfectly-rated episode?

That's the (welcome) challenge facing Fringe this week, as our critic couldn't say enough good things about "Reciprocity."

The Fox drama will tackle this mission with "Concentrate and Ask Again," an hour that focuses on the CDC calling in the team to investigate the death of a scientist with disintegrated bones. Look for someone from Walter's past to play a role on the installment, which is previewed here:

Matt Richenthal is the Editor in Chief of TV Fanatic. Follow him on Twitter and on Google+.