Missions are never as simple as they seem on Marvel's "Agents of S.H.I.E.L.D." It's a lesson Bobbi Morse (Adrianne Palicki) and Lance Hunter (Nick Blood) should keep in mind. After the two super-spies stowed away on Gideon Malick's aircraft, Bobbi is forced to go undercover in Siberia to discover his true agenda. However, complications soon arise that put Bobbi and Lance's love for each other -- and their allegiance to S.H.I.E.L.D. -- to the ultimate test.

WATCH: Bobbi and Hunter Track Malick to Russia in New Scene From "Parting Shot"

Ahead of tonight's all-new episode on ABC, "Parting Shot," Palicki and Blood spoke to CBR News about Bobbi and Nick's rekindled love, why their characters have hit a home run with audiences, the threat the new Inhuman assassin represents and how Brett Dalton's Ward brought Bobbi and Lance closer together.

CBR News: How did Ward kidnapping and torturing Bobbi really put her and Lance's relationship into perspective?

Adrianne Palicki: I think it did it in a huge way on multiple levels. For Bobbi -- having been so militant and such a soldier for so long -- it really put things into perspective for her. She had a bit of PTSD from it, but also that loss of Lance and being put in that situation made her reflect on the fact that she really needs him.

Nick Blood: They obviously work in a dangerous environment most of the time, but there's always a bit of distance between them and it. It's never been quite so present for both of them where it was one of them getting shot and possibly dying. They get some perspective and I think certainly for Hunter, that's the impetus to maybe get out of there. Nothing is more important than each other's safety.

What does it mean for both of them to be part of S.H.I.E.L.D. and how do they attack things differently?

Blood: Hunter was always a reluctant team member, but, then despite himself, he's developed an appreciation for S.H.I.E.L.D. and the loyalty to them, particularly the people he works with rather than the institution itself. I don't know if he would say it out loud, but he certainly developed a loyalty to them and perhaps got more out if than he ever thought he would. Ultimately, he is a bit of a lone ranger and wants to have a life with Bobbi. That doesn't seem possible within S.H.I.E.L.D.

Palicki: Bobbi is a soldier. She's been part of the team for a very long time. She's very structured and serious when it comes to the job at hand. Even with some of the controversial stuff that happened last year with S.H.I.E.L.D. 2.0., Bobbi always does what she thinks is the right thing, which is coming from a good place. The shift that happened was definitely the Ward thing because I think that put her in perspective, as well as losing her ability to fight, which is such a huge part of her entire existence. It got her to reflect on what's next and what else is out there.

In some ways, going undercover in tonight's episode is almost quality time for these two. How does this mission bring them closer together?

Blood: Well, they are literally sitting next to each other, so they are very close to each other. [Laughter] They have already consummated their relationship on many occasions, so they are as close as they can be. They are already skin-on-skin close.

RELATED: "Agents of SHIELD" Showrunners Tease Hive's True Nature, Bobbi & Hunter's Future

Agent May previously told Lance they aren't friends. What does he learn from pairing up with her again?

Blood: That they can learn to love each other again. No, she realizes from him that he does mean what he says. Lance is willing to make that sacrifice for the rest of the team. I think they begrudgingly respect each other.

What makes this new Inhuman assassin they face such a deadly adversary?

Palicki: When it comes to Inhuman invisibility, it's a scary feat because you never know where somebody is, especially during a fight. Hint, hint.

The writers also incorporated the Darkforce which figured prominently in "Agent Carter's" second season.

Blood: At the end of the day, with a long-running show like this, you have to be prepared to mix it up. Every season, the writers do a great job of trying to bring in new themes and to take the show in a different direction. Every season, you get a shift like that and this year has been darker.

When both your characters were introduced, it could have been for one or two episodes. They could have been killed. Why have Bobbi and Lance emerged as fan-favorites and what have you enjoyed most about their dynamic?

Palicki: I know having the character Mockingbird come on the show was a really big deal for fans. Everybody has been so supportive, which I'm very flattered by. But, I think a big portion of it was these two characters and their banter back-and-forth. It adds a different element to the show. It almost adds a light-hearted "Mr & Mrs. Smith"-type function.

Blood: It's hard to say. You are obviously very conscious of fans of Marvel Comics that have a passion and ownership over the characters. A lot of it is driven by the fans. There's an argument that "Agents of S.H.I.E.L.D." would never have happened if it wasn't for the love and support that Clark [Gregg] got for his character in "Avengers." I know I was very much like, "I've got to hope they like me," because if the fans don't like you, they'll make it known.

I think we're lucky to have the writers that we do. It's always about the way you can bounce off each other. A character might have a quality or a trait that viewers love, but that comes from the script and working opposite other actors. It's nice that they enjoy it, but it's a group effort.

Marvel's "Agents of S.H.I.E.L.D." airs Tuesdays at 9 p.m. on ABC.