Intrigue

Amy and Howard work in the lab together causing Sheldon, Bernadette and Raj to feel jealous and lonely. Penny starts using a parenting book to control Sheldon's behavior.

During a group dinner with the gang, Bernadette thanks them for letting her put Halley in Leonard and Penny's room, even though she did throw up on Leonard's Ewok. Amy doesn't want any Ewoks in her bedroom and draws the line at Sheldon's Chewbacca. Amy is working on a way for controlling robotic limbs with brain waves. Howard makes a helpful suggestion to enhance sensitivity and then agrees to work with Amy.

Leonard comes down the hall and finds Penny reading a parenting book. No, she is not pregnant. Sheldon comes in and wants a ride since Amy is working odd hours with Howard. Leonard said that it's fine since he has been driving him for years. Unfortunately Sheldon has a new car game where he imitates sirens.

Howard is drooling over all of Amy's fancy new lab equipment and her coffee maker. He inspects her cap device that is used to map the brainwave output so she can control anything. Howard quips that from that ring on her finger, she has gotten good at controlling robots. Amy warns him that that is her finance and she can control him to hurt Howard.

Leonard is getting a headache as Sheldon keeps imitating various sirens. Leonard finds it interesting that Amy is working together with Howard. Sheldon is neutral on the subject. Normally he tunes Amy out when she complains about her co-workers, but he joins right in complaining about Howard. He denies that he is complaining of Howard. He denies that is jealous of engineers, except those who run a train. Then Sheldon starts to imitate train whistles to Leonard's disdain.

Amy and Howard are working together when Sheldon shows up to check up on them. Amy was happy to see him. Sheldon starts blinking so that they can talk about Howard in front of him. Amy doesn't know Morse code and doesn't want to participate. Howard stands up and says that if you want to say something, say it in front of him, but Howard's Morse code is too rusty to understand Sheldon.

That night in apartment 4A, Sheldon is complaining that Amy says that she will return at around eight which is too inaccurate for Sheldon. Penny invites Sheldon for dinner, but he declines. With Amy not home, Sheldon is frustrated. Penny says that it is okay to be frustrated using her new parenting skills. Sheldon agrees as Penny says that his feelings are valid. Penny continues. "Now go wash up and we'll call you when dinner is ready." Sheldon leaves happy. Leonard is amazed and asks if she was a witch. Penny explains that Bernadette's book works, but only up to age five.

Raj visits Bernadette and complains that Howard had been at work every night this week with his work wife. Bernie thought that Raj was his work wife. Raj wanted to know if there was anything he could do for her. Howard has been missing some of his chores since he was away. Howard is excited about his work and Bernie is proud of him, though is still pregnant and has a lot of work to do.

Amy gets home and Sheldon asks about her day until she mentions Howard. He plans to pamper her and gets Amy her notebook they had on the project THEY had been working on together. Sheldon wants them to work on it, while Amy is tired. Finally he bugs her enough that she agrees to work on it in the morning. Sheldon gets mad and wants Leonard to drive him to Bernadette. Penny goes to check the parenting book. The advice is to give him options that are acceptable to oneself. Leonard gives Sheldon the options of driving him in two hours or taking an Uber. Sheldon chooses the Uber to both of their surprises.

Visiting Bernadette, Sheldon complains about them working together on a weekend. His presence is bothering Bernadette. Sheldon wants Howard to feel as angry as he is, so Bernie suggests that he make Howard jealous by doing something he loves to do. She tells him how much Howard loves to do chores. Before that she asks if he ever read "Tom Sawyer". First she gets him to change the batteries in the smoke detectors.

While working on the software, Howard tells Amy to check the brain model. Inside was the playing card she had chosen earlier. Amy is ecstatic. While waiting for the software to compile, Howard suggests that they put on some Neil Sedaka songs. They start to sing and dance to "Calendar Girl". Raj catches them when they said that they were working.

Back at Bernadette's, Sheldon has changed the batteries in the smoke detector and has done the laundry. Sheldon thinks that Howard will be steamed like his shirts were. Next she has him clean the oven while she sits with her feet up eating ice cream out of the tub. Raj then shows up with his news about Howard and Amy having fun. Sheldon breaks in that Howard won't have any fun after he finds out Sheldon did all his favorite chores. Raj bursts that myth. Sheldon realizes that Bernie played on his own gullibility and would storm out, but he hasn't finished cleaning the oven yet.

Now Sheldon is complaining to Leonard and Penny about Bernadette; Leonard explains that Amy and Howard working together is not a big deal. Sheldon is worried because Howard has Amy laughing and listening to music. Penny says that she is proud that he is expressing his feelings which calms Sheldon. Penny adds that everyone gets mad, even mommies and daddies. Leonard doesn't like the way Penny was handling Sheldon and then she starts learning her new parenting knowledge on Leonard. He tells Penny not to use the book on him as Sheldon picks up on what's going on. He shouts that he won't be treated as a child and then storms out of the apartment.

Later Penny asks Leonard if that is the way he was going to handle their children by throwing her under the bus. She claims that some things she is just smarter at. And no sex tonight.

Amy gets a text from Sheldon that he is upset with Leonard, Penny, Bernadette and Mark Twain. Bernadette told Howard that Raj was getting on her nerves. Amy thinks it is late and then tries to look at her watch which is now on her mounted skeleton. She is shocked and shouts "How is that even possible!" as Howard looks smug.

Raj is now hanging out with Sheldon planning to watch TV. Sheldon agrees and then tells Raj who the killer is.

Title reference: Amy and Howard's collaboration contaminating Sheldon and Raj's moods.