FBI Season 5 Episode 17

To aid Scola in his undercover mission to find the terrorists believed to be behind the imminent attack in New York City, Maggie calls in Remy, whose well-connected informant from a prior case may be key to moving the operation forward.

The crossover starts on FBI: International S02E16 Imminent Threat (I). It continues on FBI: Most Wanted S04E16 Imminent Threat (III).