Tonight, "NCIS" will return from its brief winter hiatus with a case involving a stolen drone and an elusive terrorist. 

In "Kill Chain," Susanna Thompson ("Arrow") will return as Hollis Mann, Gibbs' (Mark Harmon) ex-girlfriend. She comes into the picture when a stolen drone is linked to the terrorist Parsa. The NCIS team partners with the Department of Defense, which includes Gibb's ex, to track down the drone before it is used for a large-scale attack. 

Tony (Michael Weatherly) believes an alien airship killed the victim in the case after looking at Bishops's (Emily Wickersham) sketch. 

Meanwhile, McGee (Sean Murray) hesitates to ask for time off to attend a black-tie gala that is honoring his girlfriend, Delilah (Margo Harshman). 

Wickersham's character, Bishop, has quickly become part of the team, and is widely liked by the viewing public. However, her debut was quite a transition for the show following Agent Ziva David's departure. Wickersham spoke to TVLine about the transition and her quirky new character. 

Wickersham said she knew it was not going to be a seamless transition. 

"I think everyone knew it was going to be a bit of a bumpy start, but the writing is so great here and the way they wrote Bishop was so wonderful. She's not an intimidating character. She's really excited to be here," Wickersham said. "She's determined. She's charming in her own weird ways. I think she's non-threatening, which I hope comes across."

Bishop is an intriguing character, as little is known about her backstory so far. 

"Ellie is from a big family in Oklahoma, a Midwestern girl.... We know that she is married, though we don't really know much about Bishop's husband yet," Wickersham explained. 

"She has three older brothers,which I think makes the transition to hanging out with the "NCIS" crew easier. She's used to being surrounded "by the guys," she continued. 

Executive producer Gary Glasberg hinted that Bishop is not as perfect as she seems. Wickersham said her faults will soon come to the surface. 

"I know what he [Glasberg] was referring to, but it's something I don't think I can talk about yet," she said. "For me, I think the faults in people are the most interesting and fun things to play. Like anyone, she's got her weaknesses for sure. Even though she's usually very on top of it, there are definitely weaknesses and faults that'll pop out."

She also revealed that Bishop knows how to use a gun. 

"She's gone through (...) NSA weapons and field training. That was actually something that I had to do before I started here. Our tech advisor, Leon Carroll, took me to the gun range. I had never held a gun in my life, so I was terrified," Wickersham shared. 

She also said that unlike her calm character, she was nervous about joining the long-running series. "I guess Ellie was nervous about joining the team, but I was really nervous about joining "NCIS" just because it's been around for a while. Coming into that was really intimidating and scary. I'm a nervous person, so that was a very, very big thing!"

"Kill Chain" airs Tuesday, Jan 7 at 8 p.m. on CBS.