Plot
A papillon named Sophie is taken to the veterinarian's office by her owner for a bordetella vaccination. Her owner worries that Sophie is frightened from her previous experience of getting a shot and will hold a grudge on her for this one. However, the veterinarian explains that dog memories work differently from human ones, so she will likely forget today's experience in a couple of days.
Later, Sophie is taken into a faraway house by a man. She is very afraid and confused, as she does not remember what her life was like previously or where she is going. The man leaves her with his eight other dogs, who eagerly surround the new dog. A shepherd mix named Rusty pulls her away from them and introduces her to everyone. The dogs show Sophie around the house, which is decorated with taxidermied wildlife. After she has an accident out of fear, Rusty comforts her by saying that she is safe here and the master will not abandon her like her previous owners.
Seeing Sophie hiding and shivering under a table, the man wraps her with a red scarf. Sophie sniffs the scarf, and realizes that it belonged to her owner. Sophie remembers that the man broke into her owner's house, then strangled her to death with her own scarf when she returned home. Sophie attempts to tell the other dogs that their master murdered her owner, but they do not believe her, especially Earl the hound. That night, she has a nightmare about her owner's death. When Rusty wakes her up to offer aid in figuring out the truth behind her story, Sophie does not understand what he is talking about. Rusty brings Sophie the scarf, restoring her memory.
During breakfast time, Sophie and Rusty decide to explore the master's private room while the man and one of the dogs, Aldo, are away. They enter the room, finding it full of women's clothing and various photographs of women. The man returns; while Sophie hides in a box, the man forces Rusty out and locks the door. The man works in his private room until he hears Rusty damaging objects in the living room. While he locks Rusty in the backyard shed for punishment, Sophie escapes the room. After Rusty is removed from the shed that evening, Aldo states that the man spent his day meeting a lady and taking pictures of her. Sophie asks if a photo she got from the private room was the woman; Aldo says it is not, but an Alaskan Malamute named Roxanne recognizes the woman as her owner and remembers that she was killed.
While the other dogs go inside for supper, Roxanne smells something from under the porch. She moves a shovel, causing a small door to swing open. Roxanne, Rusty, Sophie, and Victor the Dalmatian go through the door, and see piles of dirt that they suspect are graves. Roxanne begins vigorously digging despite Rusty's warning that the man is coming. When the man investigates the open door, the dogs hide in a hole until he leaves to feed the other dogs. The dirt-covered dogs reunite with the other dogs inside, having found a scrap of clothing. The dogs (except for the skeptical Earl) sniff the scrap. Victor recognizes it as part of his second owner's firefighter uniform, and remembers that the man strangled her with his bare hands while Victor was tied to a table. Victor presses the 9-1-1 button on the man's landline and has the other dogs bark to get help. Sophie watches Earl climb upstairs and warn the man by pawing at his private room door. The man comes downstairs and explains to the emergency operator that his rowdy dogs accidentally knocked the phone over. He then takes Victor out to the shed, and dogs hear a gunshot.
The next morning, the man leaves the house without feeding the dogs. Everyone except for Earl believes that Victor has been shot dead and that they are next. Earl and Sophie question each others' memories, and the other dogs turn on Earl after Sophie reveals he ratted the dogs out during their phone call and Rusty claims to remember the killing of his owner. The dogs then go to the backyard to figure out Victor's fate. They smell his blood behind the shed, and Sophie enters it, finding Victor's skinned hide. The dogs immediately try to escape, but they cannot climb over or dig under the chain link fence of the backyard. They attempt to escape through the front, but they cannot unlock the door. Earl enters the private room, remembering that the man entered his owner's room when he was a puppy and fed him treats to distract him while he strangled his owner. Earl opens a cabinet with the taxidermized heads of Victor and the dogs who Earl grew up with in the house.
The man enters his private room, loads a shotgun, and commands Earl to leave the room; instead, Earl bites the man's neck. Earl runs out and warns the others to run while Imogene the Tibetan mastiff shoves the pursuing man. Earl breaks through the front window, allowing the others to exit the house. Sophie stays behind to look for the scarf so she does not risk forgetting again, but runs out to bite the man's leg so he stops shooting at the others. Earl runs into the highway in front of the house, getting hit by a car and causing a pile-up that forces the other cars to stop. Earl dies from his injuries, and the dogs mourn. The man bleeds to death from Earl's bite wound.
Police officers come to investigate the crash. The dogs alert a K9 to the bodies under the back porch, so the police dog leads the officers to them.
Four months later, Sophie, now having been readopted and renamed Trudy, is running at a park. She reunites with Rusty and they happily play together, not mentioning their experience in the man's house. When it is time to go home, Trudy briefly hesitates before happily leaving the park with her owners.
