"I want him to believe in love, because it is the most important thing... but you need to show him. Promise me!"
Haley Hotchner (neé Brooks) was a recurring character who first appeared in the show's pilot Extreme Aggressor as the wife of SSA Aaron Hotchner. At the time of her death in 100, she and Hotch were divorced.
Background
Haley and Hotch met in high school. She was in the theater club and was rehearsing a role in Gilbert and Sullivan's The Pirates of Penzance when Hotch walked in by mistake and fell in love with her, even taking a minor part as "Fourth Pirate" to be close to her.
On Criminal Minds
Together they have a son named Jack. Their marital issues were a running theme and by the end of "In Name and Blood", it looks as though Haley and Jack have left. At the end of "Scared to Death", Hotch mentions to Morgan that he isn't sure if Haley is coming back. At the end of "Birthright", Haley has Hotch served with divorce papers as he is leaving the office for the day. He signed them in Damaged. Haley continued using her married name, Hotchner, but it is revealed that Hotch kept her listed under "Brooks" in his personal information just in case it got into the wrong hands.
In the Season Five premiere, Nameless, Faceless, Haley and Jack are suspected to be potential targets of George Foyet. After Hotch is found at a local hospital, the team races to find Haley and Jack. Haley is found folding clothes in her bedroom, and Jack is spending time at a friend's house on a "play date". Haley is taken to safety, and Morgan offers to pick up Jack. When the two are safe, they are taken to Hotch's hospital room. Hotch tells Jack that he loves him and that they will have to go away for awhile. He tells Haley that he will spend the rest of life making it up to her, and once Foyet is caught, they can return home. They are later placed in the protective custody of U.S. Marshal Sam Kassmeyer.
In the episode 100, Haley is found by Foyet after he murders Kassmeyer and is held at gunpoint by him as she calls Hotch when she believes him to be dead, having been told so by Foyet, who had been using an alias at the time. Hotch tells her not to show fear and that she is brave even though she knows she will be killed. Foyet then presses a gun to the back of her head. Hotch apologizes to Haley for putting her and Jack into this mess before a gunshot is heard echoing through the phones as Hotch is on one line and the rest of the team is on another.
Hotch comes into the house to find Haley dead, lying covered in blood on the floor of their old bedroom. Hotch, in a rage, eventually beats Foyet to death in revenge for Haley and all of Foyet's other victims. Her funeral was held in The Slave of Duty, at which Hotch delivers the eulogy, reciting a passage from Act II of The Pirates of Penzance as well as a quote by one of its writers, W.S. Gilbert.
Haley reappears in Route 66 as a hallucination fabricated by Hotch when he begins having severe complications brought by his stabbing at the hands of Foyet. She first appears in a movie theater, greeting Hotch and inviting him to sit down next to her. He does so, and together, they watch a movie about Hotch's recent life, in which she compliments Beth Clemmons, Hotch's current love interest. They are joined by Foyet himself, and despite him shooting her in the stomach with his revolver (not visibly affecting her), she displays a welcoming attitude towards him. When the movie ends, Hotch declares that he wants to come with her, but Haley tells him that Jack and Beth need him. After Foyet leaves, Haley tells Hotch that Beth is "a keeper" and that he "better not mess it up". She then tells him she still loves him before leaving. In the week following his near-death experience, Hotch puts up a photo during a "Day of the Dead" celebration hosted by Garcia.