If you learn one thing from tonight's Agents of SHIELD's "Watchdogs," it's that only one person can call Mack "Alfie."

The departure of Bobbi (Adrianne Palicki) and Hunter (Nick Blood) hit Mack (Henry Simmons) hard, and the agent will take a little vacation time to deal with the loss of his workplace BFFs.

"Mack comes back and because he's wounded because Bobbi and Hunter left, I think he wants to repair some other relationships," Simmons told EnStars at WonderCon.

Mack's time off will cause him to reunite with his brother Ruben (Gaius Charles), and, due to the nature of the agent's job, the pair will be on rocky ground.

"One thing we talked about before is SHIELD is like being in the CIA. The thing is, you can't tell people I'm in SHIELD, [that] I'm part of SHIELD," Simmons explained. "What the writers wanted to do was explore the other side of SHIELD when you're not working, your personal history with your families and things of that nature. You're gone for a long time...you miss everything, and you have to come up with poor excuses as to why. It causes strained relationships and that's what you see."

The brothers won't have too much time to bicker, however. A anti-Inhuman militia has set up shop in the MCU, and Mack and Fitz will find themselves in the middle of Daisy's quest to take them down.

"When a radical group called The Watchdogs emerges with plans to eliminate the Inhumans, Agent Mack and his brother become caught in the crossfire," ABC teased. "Meanwhile, Simmons discovers a powerful chemical compound that could alter the future for Inhumans.

Meet Ruben when Agents of SHIELD airs tonight at 9 p.m. ET on ABC. Click the video below to see a sneak peek and a preview for "Watchdogs."

Tags: Marvel's Agents of S.H.I.E.L.D. television ABC Marvel WonderCon 2016