02E10 - Arrivals and Departures

Walter's Irish parents Sean and Louise O'Brien visit Megan whose condition nears terminal. Then a fatal fungus outbreak in the hospital cuts Walter off from his sister, placing the whole team at risk. Assuming it's Stachybotrys, the infectious disease unit searching for a cure collapses by spraying the wrong fungicide, requiring Scorpion to search for a cure. Toby examines natural fungicide gold dust on a cafeteria worker's boots and sees the man cut his leg, becoming a host to Meliola Anfracta, an ancient fungus unearthed in soil. Sylvester's OCD about using antibacterials ironically caused him to grow a super-bacteria on his hands that is fatal to the fungus. With help from Ralph and Cabe, who the CDC keep outside, they spread the bacteria through the water standpipes to save those trapped inside. Walter reaches Megan just before she dies. Later, by emailed video Megan reminds him that he is not just his brain, and he should not be afraid to love. Walter begins to open up to his estranged parents and holds hands with Paige while sharing family memories.