Catherine Rollins' (Michelle Borth) life will be put in danger in Friday's episode of Hawaii Five-O and Adam (Ian Anthony Dale) will make the ultimate sacrifice to save Kono (Grace Park).

A teaser video for the upcoming episode titled, Kupu'eu, labeled it as the one "that will change everything." It also includes the tagline, "A hero will fall."

Catherine gets shot in the midst of a surveillance assignment and viewers see her battling for her life in the hospital as her boyfriend, a despondent Steve McGarrett (Alex O'Loughlin), sits by her.

It has also been suggested that Adam will take a very radical step that might put his life in danger to save Kono. The Oct. 18 episode revealed that Kono was also on the enemy's hit list with Adam. When Chin found out about this, he said that she needed to get out of Hong Kong right away and told Adam to do whatever it took to save Kono.

In another sneak peek from the forthcoming episode, Danny is riding through a rugged terrain with Joe. The two joke about the condition of Joe's car and while Danny tries explaining how much of wreck it is and that Joe might need to get the suspension checked, Joe assures him that the car is in perfectly good shape.

As Danny continues on about that, Joe asks him if that is what he and Steve do when out on assignment, "bicker like an old married couple." Danny tells him they don't "bicker," they just "argue" from time to time.

They then move on to more serious conversation in which Joe says Steve asked him to get in touch with Doris (Steve's mom). He suggests Doris is missing and that it seems like some of her old enemies might have been on to her whereabouts. When Danny asks if Joe thinks she is on the run, Joe said the situation could be worse.

Season 4 of Hawaii Five-O continues Friday, Oct. 24, at 9 p.m. E.T. on CBS.

Watch the promo for episode 5 here:

Watch the sneak peek featuring Danny and Joe:

Tags: Hawaii Five-O Season 4 episode 5