It was actually seeing his face that did it, so maybe they both would've been better with the mask on because it came as a sob that she stifled with her hands pressed over her mouth. The move would have been comical if there hadn't been another to follow it and then one more before the flood gates opened and there were tears streaming down her cheeks. She held her mouth with one hand and scrubbed her eyes with the other, embarrassed and annoyed and just so happy to see him. Because she was always pretending to be so strong like it didn't hurt a little to leave her mom and to come here, like it didn't hurt to lose Billy and Teddy and the others, like she wasn't a completely selfish brat to just abandon Kate and Cap and Tony. She hadn't expected to be gone so long, not at all. Cassie had thought she'd be back and then, when everybody started dying, she convinced herself she didn't need to come back, she didn't need these people like she hadn't needed them back home. She was a hero, heroes didn't need anyone, heroes saved the world and when they had to start over they did.
Except she hadn't felt like a hero since she'd left, she'd been feeling really small (and no in any way she was used to) and Tony's face reminded her that there were real heroes and she did need them and she actually needed him even though he was an asshole a lot and she was an even worse asshole right now because she'd hoped she'd find her Dad in this universe and she then hadn't, but really unexpectedly she'd managed to find herself a surrogate and then up and left him. But now he was standing right here. Probably she should've told him all of that or apologized or something but instead she kept on scrubbing her eyes and trying to breathe and finally croaked out, "Hey, I missed you."