If you get squeamish when you see a rat, you may want to shield your eyes. We’re being serious!

The Zoo team, led by zoologist Jackson Oz (James Wolk), become the unexpected victims of a terrifying infestation of rats in Tuesday’s all-new episode of the CBS summer drama, in a scene exclusively debuting on ETonline.

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And when we say infestation, it’s not just a dozen or so of those critters scurrying down a corridor, it’s hundreds.

The cause of such a traumatic sight? A cargo ship carrying the “bloodthirsty rodents” washes up off the coast of Massachusetts.

As the gang explores the abandoned building, the lights start to flicker on and off. When they hear an elevator ding, they feel relief. “Must be Becky (Scottie Thompson),” Jackson says with an ounce of hope that the sheriff has arrived.

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Instead, what awaits them is something far more cringe-worthy than that. Watch the clip above to find out what happens next!

Zoo airs Tuesdays at 9 p.m. ET/PT on CBS.

Find out why Zoo is one of ET’s must-watch TV summer picks!