"Alone" is the first episode of the fourth season of House and the seventy-first episode overall.
When an office building collapses, House has to work fast to diagnose a young woman, Megan, who survived the disaster. Due to her injuries, Megan's only form of communication is blinking with one eye.
In typical fashion, House's first instinct is to break into Megan's home to look for clues (tricking Wilson into joining him by telling him that he would take him to a restaurant for lunch). House discovers her diary and deduces that she must be on antidepressants. When confronted with this by House, Megan's boyfriend and her mother complain to Cuddy, who agrees with the diagnosis. However, the diagnosis fails as new symptoms continue to appear.
Throughout the episode, Cuddy and Wilson try to convince House to hire a new team, while House keeps insisting that he doesn't need one. Instead, he tries bouncing ideas off of a janitor, and even gives the janitor a white coat and has him pose as a doctor to Megan's boyfriend and mother. In an attempt to prove to House that he needs a team, Cuddy sends a memo out banning anyone in the hospital from assisting him in his diagnosis. Meanwhile, Wilson "kidnaps" House's guitar and leaves a ransom note.
House walks down to the E.R. where he begins to ask any doctor within sight about his patient's symptoms and what might be the cause. Nobody will respond except for a young female doctor. House notes that her caring demeanor "reminds him of someone," presumably Dr. Cameron. During his conversation with her, he decides it must be two separate conditions. When Cuddy discovers a doctor working on a diagnosis House has made regarding Megan's possible alcoholism, she discovers House has sent out a second memo from her e-mail telling staff to ignore the first memo. He also convinces a cancer patient of Wilson's to move to a different room so that Wilson will think that the patient was kidnapped.
House makes several startling revelations about the patient that surprise her boyfriend and mother. Her boyfriend believed that she wanted to have children and they were trying to do so. House states that she has had an abortion and apparently lied to him about it. The patient is also a heavy drinker, something which shocks both of them. House continues to give treatment based on the woman's condition and medical records, none of which work, and her condition continually worsens.
Wilson then charges into House's office and demands to know where the moved cancer patient is. He says that if his patient gets the wrong medication due to the wrong chart, he could die. This triggers House to realize that the patient he has been treating has been getting the wrong medication because it is the wrong patient. House wakes the patient from her comatose state using amphetamines and asks her name. The woman struggles, but finally says "Liz". Liz is actually Megan's co-worker who worked in the same area of the office building that collapsed. Both have the same hair color and build, and their faces were badly injured when the building collapsed, allowing them to be incorrectly identified by their families. The real Megan died elsewhere in the hospital with Liz's boyfriend by her side.
Cuddy comes into House's office to talk about the case. She mentions that while House did solve the case, he would have solved it much earlier if his team was in place, as Cameron would not have accepted that a boyfriend would have known so little about the love of his life, and when House diagnosed multiple conditions, Foreman would have worked hard to prove House wrong, while Chase would have worked harder to prove House right; this is the first time the three deposed team members are mentioned by name in the episode despite multiple conversations about them. House apparently realizes the validity of Cuddy's point and decides to hire a new team, though he will do it his way. The episode ends with a close up of House strumming a small tune on his guitar, prepping his new recruits, who turn out to be a room of 40.