Highlights from the Twentieth Episode of Season 4 of Hawaii Five-0

The investigation of a murdered pool cleaner leads Five-0 to uncover a possible terrorist cell of radicalized students who are plotting an attack on U.S. soil.

Season 4 Episode 20 Photos - Hawaii Five-0

Season 4 Episode 20 Photos - Hawaii Five-0

The investigation of a murdered pool cleaner leads Five-0 to uncover a possible terrorist cell of radicalized students who are plotting an attack on U.S. soil, on HAWAII FIVE-0, Friday, April 25 (9:00-10:00 PM, ET/PT) on the CBS Television Network. Pictured Daniel Dae Kim as Chin Ho Kelly Photo: Best Possible Screen Grab/CBS /©2014 CBS Broadcasting, Inc. All Rights Reserved
Under The Sea in “Pe'epe'e Kānaka” S4 E20

Under The Sea in “Pe'epe'e Kānaka” S4 E20

The investigation of a murdered pool cleaner leads Five-0 to uncover a possible terrorist cell of radicalized students who are plotting an attack on U.S. soil, on HAWAII FIVE-0, Friday, April 25 (9:00-10:00 PM, ET/PT) on the CBS Television Network. Pictured Daniel Dae Kim as Chin Ho Kelly Photo: Best Possible Screen Grab/CBS /©2014 CBS Broadcasting, Inc. All Rights Reserved
But How Did He Do It? in  “Pe'epe'e Kānaka” S4 E20

But How Did He Do It? in “Pe'epe'e Kānaka” S4 E20

The investigation of a murdered pool cleaner leads Five-0 to uncover a possible terrorist cell of radicalized students who are plotting an attack on U.S. soil, on HAWAII FIVE-0, Friday, April 25 (9:00-10:00 PM, ET/PT) on the CBS Television Network. Pictured (l-r) Grace Park as Kono Kalakaua , Alex O’Loughlin as Steve McGarrett and Masi Oka as Dr. Max Bergman Photo: Best Possible Screen Grab/CBS /©2014 CBS Broadcasting, Inc. All Rights Reserved
It Can't Be True in “Pe'epe'e Kānaka” S4 E20

It Can't Be True in “Pe'epe'e Kānaka” S4 E20

The investigation of a murdered pool cleaner leads Five-0 to uncover a possible terrorist cell of radicalized students who are plotting an attack on U.S. soil, on HAWAII FIVE-0, Friday, April 25 (9:00-10:00 PM, ET/PT) on the CBS Television Network. Pictured Alex O’Loughlin as Steve McGarrett Photo: Best Possible Screen Grab/CBS /©2014 CBS Broadcasting, Inc. All Rights Reserved

"Pe'epe'e Kānaka” S4 E20

The investigation of a murdered pool cleaner leads Five-0 to uncover a possible terrorist cell of radicalized students who are plotting an attack on U.S. soil, on HAWAII FIVE-0, Friday, April 25 (9:00-10:00 PM, ET/PT) on the CBS Television Network. Pictured (l-r) Grace Park as Kono Kalakaua Photo: Best Possible Screen Grab/CBS /©2014 CBS Broadcasting, Inc. All Rights Reserved
“Pe'epe'e Kānaka” S4 E20

“Pe'epe'e Kānaka” S4 E20

The investigation of a murdered pool cleaner leads Five-0 to uncover a possible terrorist cell of radicalized students who are plotting an attack on U.S. soil, on HAWAII FIVE-0, Friday, April 25 (9:00-10:00 PM, ET/PT) on the CBS Television Network. Pictured (l-r) Scott Caan as Danny “Danno” Williams and Alex O’Loughlin as Steve McGarrett Photo: Best Possible Screen Grab/CBS /©2014 CBS Broadcasting, Inc. All Rights Reserved
“Pe'epe'e Kānaka” S4 E20

“Pe'epe'e Kānaka” S4 E20

The investigation of a murdered pool cleaner leads Five-0 to uncover a possible terrorist cell of radicalized students who are plotting an attack on U.S. soil, on HAWAII FIVE-0, Friday, April 25 (9:00-10:00 PM, ET/PT) on the CBS Television Network. Pictured (l-r) Scott Caan as Danny “Danno” Williams and Alex O’Loughlin as Steve McGarrett Photo: Best Possible Screen Grab/CBS /©2014 CBS Broadcasting, Inc. All Rights Reserved
“Pe'epe'e Kānaka” S4 E20

“Pe'epe'e Kānaka” S4 E20

The investigation of a murdered pool cleaner leads Five-0 to uncover a possible terrorist cell of radicalized students who are plotting an attack on U.S. soil, on HAWAII FIVE-0, Friday, April 25 (9:00-10:00 PM, ET/PT) on the CBS Television Network. Pictured (l-r) Alex O’Loughlin as Steve McGarrett, Daniel Dae Kim as Chin Ho Kelly and Scott Caan as Danny “Danno” Williams Photo: Best Possible Screen Grab/CBS /©2014 CBS Broadcasting, Inc. All Rights Reserved