"Mercy" is heating up with the assisted-suicide death of Sonia's (Jaime Lee Kirchner) private patient; Veronica (Taylor Schilling) and Dr. Sands (James Tupper) back in the sack; and Chloe (Michelle Trachtenberg) learning some truths about the arrogant Dr. Briggs (James Van Der Beek), the newest member of the hospital staff.

"[James Van Der Beek] insists on having this sort of fan that blows your hair back when he is doing surgery. I know about it from The WB promos," jokes Michelle, who was on The WB's "Buffy the Vampire Slayer" at the same time James was on "Dawson's Creek." "I have known James for years. He is whipping us into shape. If there were any laziness that had seeped into the later part of the season, he has been with a whip: 'Come on. I know your lines, too.'"

On the more serious side, Guillermo Diaz, who plays Angel Garcia, tells ET that James has blended into the show seamlessly, but it remains to be seen if he will become a regular cast member if "Mercy" gets picked up for a second season.

"Mercy," of course, is full of medical emergencies, but they aren't all scripted.

"During production, I found out that I am severely allergic to what is inside the latex surgical gloves," Michelle tells ET. "It was probably in episode 10, because the kind of nurse that Chloe is doesn't do a lot of surgery. On the packaging, it says: 'Caution. May cause severe allergic reaction.'"

And that is just what happened. Michelle broke out in hives and needed to take Benadryl, but she wasn't gung-ho about the idea because of an earlier experience with the drug.

"Right before we started filming the show, I got a bee sting," she recalls. "I am very naïve when it comes to drugs. My system is untainted, and when that Benadryl hit my system, it was: [she slurs] 'Hello doctor. Who makes your scrubs? Your scrubs have a black drawstring, I like it.' I had a nurse who had this amazing unicorn tattoo, say, 'Let's lay you back down.' It wasn't even morphine, it was Benadryl!"

"Mercy" airs tonight at 8 p.m. on NBC.