But once he's in the hallway, Mark's cool demeanor collapses. He sinks onto a seat and grabs the bridge of his nose, blinking away tears and choking back nausea. His eyes redden.

Mark escapes outside for some fresh air, popping an aspirin and sinking tiredly onto a bench in the ambulance bay. He's clearly weak. Susan approaches and scolds him for still being on his feet attempting to work. "Do you have a headache?" she softens. "Just a little stress," Mark downplays, all Brave Little Tumor about it. "That, and several hundred beams of radiation zapped into your brain this afternoon," Susan sighs. She wants him to go home, but Mark staunchly -- if listlessly -- wants to serve out the remaining half-hour of his shift. "Did you tell her?" Susan queries gently. Mark stares into her eyes sadly, then shakes his head. Susan's upset that Mark has kept this secret from everyone, including Rachel. Mark confesses he's scared of being treated differently, of unintentionally coloring everyone's emotions with a deep pity that could be mistaken for something more profound. "They start giving you that look," Mark mopes. "That look...like you're half-there. Like you're already gone. Believe me, I've seen it before." You've been seeing it for two years from home viewers, Mark. "Well, you're still here," Susan says dryly. God, she's prickly. Mark gazes at her, then stands quickly and bids her farewell. The motion is too much, though, and a wave of nausea knocks him back onto the bench. Susan freaks and threatens to rat him out to Weaver unless he allows Susan to escort him home. Wordlessly, Mark complies. "You better not puke in my car," Susan grouses good-naturedly. Except it's also mildly annoying. Even when she's expressing concern, Susan acts irritated. Every word of sympathy shooting from her mouth feels barbed.