Misery

Famed novelist Paul Sheldon (James Caan) is the author of a successful series of Regency romance novels featuring a character named Misery Chastain. Wanting to focus on more serious stories, he writes a manuscript for a new novel that he hopes will launch his post-Misery career. While traveling from Silver Creek, Colorado to his home in New York City, he is caught in a blizzard and his car goes off the road, rendering him unconscious. Paul is rescued by a nurse named Annie Wilkes (Kathy Bates), who brings him to her remote home. When Paul regains consciousness he finds himself bedridden, with both his legs broken as well as a dislocated shoulder. Annie claims she is his "number one fan" and talks a lot about him and his novels. As a reward for saving him, Paul gives Annie his new manuscript. While feeding him, she is angered by the profanity in the new manuscript and spills soup on him but apologizes. She buys a copy of Paul's most recently published book, Misery's Child, giving him praise. However, when she discovers that Misery dies at the end of the book, she flies into a rage. She reveals that she lied about calling his agent and the authorities; nobody knows where he is. Paul tries to escape from his room, but she has locked the door.
The next morning, Annie forces Paul to burn his latest manuscript. When he is well enough to get out of bed, she insists he write a new novel titled Misery's Return, in which he brings the character back to life. Paul complies, believing Annie might kill him otherwise. He also tells her he will use Annie's name in the book in appreciation of her nursing him back to health. When the first few chapters show continuity errors, Annie chides him angrily and forces him to start again. One day, Paul sneaks out when Annie is away and begins stockpiling his painkillers. He tries poisoning Annie during dinner, but fails. Paul later finds a scrapbook of newspaper clippings about Annie's past. He discovers that she was suspected and tried for the deaths of several infants, but the trial collapsed due to lack of evidence. Annie had quoted lines from his Misery novels during her trial. Annie later drugs Paul and straps him to the bed. When he wakes, she tells him that she knows he has been out of his room and breaks his ankles with a sledgehammer to prevent him from escaping again.[6]
The local sheriff, Buster (Richard Farnsworth), is investigating Paul's disappearance. When a shopkeeper informs the sheriff he has sold Annie considerable quantities of typing paper, Buster pays Annie a visit. When he finds Paul drugged in the basement, Annie fatally shoots Buster and tells Paul that they must die together. He agrees, on the condition that he must finish the novel in order to "give Misery back to the world". He then conceals a can of lighter fluid in his pocket.
When the book is done, he reminds Annie it is his practice to have a single cigarette and a glass of champagne after finishing a novel. After he gets them, Paul sets the manuscript on fire, giving him the chance to hit Annie over the head with the typewriter. Paul and Annie fight and Annie is killed.
Eighteen months later, Paul, now walking with a cane, meets his publishing agent Marcia (Lauren Bacall) in a restaurant in New York City. The two discuss his first non-Misery novel. Marcia tells him about the positive early buzz which Paul does not care about, saying he wrote the novel for himself. Marcia asks if he would consider a non-fiction book about his captivity, but Paul declines. While at the restaurant, he imagines the waitress as Annie. The waitress says she is his "number one fan", to which Paul uncomfortably responds "That's very sweet of you".

Question: What is the local sheriff investigating?
Answer: Paul's disappearance