Like the one that Samantha's making now, to Mitchell, to tell him that Olivia Dunham is there: "She claims she was here to check on you." Meanwhile, Olivia's searching through bills and other documents in the drawers of a rolltop desk in the living room. Over at the Fringe lab, Peter's not having any luck listening in, so he calls his buddy Kyle back: "It's not working. All I'm getting is buzz. I don't hear anything." So Peter's going to miss the crucial part: Samantha telling Mitch that she thinks Olivia knows, with Mitchell doubtful but telling Samantha she needs to kill Olivia.
After a commercial break, we see Olivia's used her lockpicks to open the rolltop part of the rolltop desk. Samantha's arguing with Mitchell about the need to kill Olivia, saying her office might know she's there. Mitchell tells her it doesn't matter: "Dunham's already under suspicion for being unstable. They think she's dangerous."
Peter, meanwhile, wraps up talking to Kyle so he can try the phone tap again.
Olivia finds pictures of the giant cold virus in the desk, and makes a satisfied "I knew it!" face and glances towards the kitchen, where Samantha's listening to Mitch telling her (and now being listened to by Peter): "We can say she came after you, that it was self-defence." Samantha says there has to be another way. Mitchell: "There isn't, honey. There's one way. You cannot let Dunham leave there alive." Peter's eyes go wide, as Mitchell tells Samantha there's a gun in the entry closet. "Contact me when it's done," he says, and hangs up.
Peter hangs up and gets on his cellphone to tell Olivia, who, while Samantha grimly makes her way to the entry closet arsenal, is putting things back and rolling down the desk. Mitchell's also already on his way out of the office. Olivia's phone vibrates -- good thing she remembered to do that, huh? -- and she quietly answers. Peter tells her to get out of the house: "Samantha Loeb is going to kill you!"
Samantha gets the gun from the closet, which is just sitting under a sweater on a shelf and not tucked away anywhere or anything, and then starts stalking through the house, holding the gun up with both hands, which would be a little awkward to explain if Olivia happened to see her. She makes her way to the living room and then back to the bottom of the staircase. She looks upstairs, and suddenly Olivia is behind her, pointing her own gun at Samantha. She orders Samantha to put her gun down, and Samantha drops it on the floor.