Chase shows House Clancy's DNA and the DNA of the heart they just biopsied. "That is impossible," House says. But after two more tests, the results have been confirmed. "The genes from Clancy's myocytes don't match the genes from the rest of his body," Cameron helpfully explains to those of us who can't read DNA. "Alien DNA!" Chase helpfully explains to those of us who still think we're watching The X-Files.
So what's the differential diagnosis for all this? Foreman suggests UV radiation mutated Clacy's genes, although House points out that Clancy would have to be exposed to so much UV radiation that he'd look like George Hamilton. Does this mean that we can look forward to George Hamilton growing an extra arm or developing some other mutant power? I hope so. Cameron suggests exposure to some chemical then tires of this exercise and starts asking House whether his leg hurts since he's leaning on the table and looking generally pained. House tells her to stay on topic. Chase suggests going in and cutting the weirdo myocytes out of Clancy's heart and then calling it a day, but Foreman and Cameron point out that they can't be sure that those are the only cells in Clancy's body with alien DNA. But how do they find the other alien DNA cells? Well, Cameron suggests "tagging" them by creating an antibody to the alien DNA's unique protein signature and then flushing the antibody throughout Clancy's body, causing the affected cells to "light up like lightbulbs," Cameron finishes, ably creating the metaphor House requested.
Wilson and Cuddy are hangin' out at the new hotspot, the second floor balcony. Cameron comes running up, shouting that they have to tell House the truth, and I'm guessing that the acoustics of the open-air lobby have now informed the rest of the hospital about this as well. Cuddy wants to figure out "another plan," and Wilson admonishes her for using the word "plan" as it implies that they're plotting against House. Which they totally are. Cameron's had enough of this and says that she's going to tell House the truth. "No, you're not," Wilson snots. Shut up, Wilson. Cameron Baldricks that they'd better come up with a "cunning plan" and storms off, leaving Wilson and Cuddy to make ashamed faces at each other. And with guilt comes anger: "she's not nearly as delightful as she thinks she is," Cuddy grumbles.