As Amy's sweet sixteen approaches, new hand Caleb is interested in asking her for a date. Amy is fascinated with the white mustang that's lost his herd but has been spotted around Heartland. Meanwhile Lou and her dad are working on plans to start an "Equine Executive Retreat" but Grandpa Jack is none too thrilled with the idea of an upscale dude ranch on his property. Mallory is lobbying to spend the summer at Heartland while her parents travel with the rodeo. And Ty's not been heard from since he left for the city to get reacquainted with his father.

Ty returns to Heartland, but he now has a rival for Amy's affections. Also, Lou and her dad go against Jack over how they're going to change Heartland.

Amy receives a horse for her birthday, which leads her to decide whether she wants to continue helping at heartland or pursuing a career in show-jumping.

Lou plans a a weekend alone with Scott while the rest of the crew go on a cattle drive for the ranch where Tim is working. Much to Scott's dismay, Lou's plans hit a snafu when a travel blogger and her husband, the first customers of the dude ranch show up a week early. On the trail things are just as rocky. Tim learns that the owner's daughter is planning on selling now that her father has died. Ty learns that the horse he's riding is blind and he's been just as much in the dark about Amy's feelings. Meanwhile Jack is having problems of his own. Lisa has given him a space-age saddle that's supposed to be good for folks with arthritis and Jack is feeling more and more like a grumpy old man.

Lou takes three of her former New York co-workers on the Heartland Equine Retreat trail ride. She ropes in Jack, Amy and Tim to assist. Ty encounters Kit Bailey for the first time. Caleb introduces Kit to Ashley Stanton in order to set her up with a training partner and a horse, as she's taken up barrel racing. Val is terribly upset when she finds out, and decides that Ashley doesn't need her show-jumper, Apollo. Mallory takes Spartan out for a ride, and loses him momentarily. When he becomes ill later on, Ty realizes the horse must have eaten pesticide-sprayed grass. With the help of Kit and Caleb, he gets the remedy down Spartan's throat, saving the horse's life. Lou's friends depart after returning from the trail ride, having each learned a little something about themselves, and each other.

Amy tries to help an RCMP horse who's become skittish around water after his constable rescues a 15 year old from drowning. Mallory asks Jack's advice about how to get rid of an unwanted boy friend... be too busy to see him. Suddenly Lisa seems too busy for Jack. Meanwhile Lou recommends Scott to the local polo team, but Scott is worried that he got the job because of Lou's relationship with the team's captain, Nick Harwell. But is either Fleming girl really ready to settle down? Lou is awfully smitten by the hunky RCMP constable and Amy still seems mighty intrigued by Caleb.

It's rodeo time and the Heartland crew is all involved. Amy decides to try team roping at the rodeo, with Caleb. When Tim's advice gives Caleb second thoughts, Ty is glad to help Amy practice, until Jack convinces Caleb to make good on his commitment and take her back. Meanwhile Lou pulls such a nutty while sponsoring Soroya for the Queen of the Rodeo contest that she loses her contestant. Ty's feeling left out but what a novice cowboy to do?

One night during a late summer heat wave Ty's dad shows up with a truck full of sick and thirsty horses bound for the slaughterhouse. As Scott and the hands at Heartland work to save the horses Lou calls the police but they can do nothing. When Amy recognizes one of the horses as Apollo, Ashley Stanton's old jumping horse, the mystery deepens. Lou looks into buying and rescuing the animals while Ashley confronts her mother and Ty warily spends some time with his disreputable father.

Mallory's dad's got a gold record and a new plan for Mallory... Boarding school. Meanwhile Amy's back in school as well leaving more of the chores to Jack, Caleb and Ty. Ashley's staying at Heartland, much to her mother's dismay, and has promoted herself to VP of guest relations. Ty is still trying to make amends with Amy for his latest relationship snafu, while Caleb likes the way things are working out. Lou's seeing more of Constable Mark because of a recent upsurge in cattle rustling.

Tim recuperates from his shooting injury at Heartland ranch, immediately trying the patience of Jack. Callie is upset when she finds out Tim has not told anybody about their relationship. Amy makes some surprising discoveries about Hank, an elderly ex-owner of a horse she's attempting to re-home. Ty convinces Amy to talk to Caleb, who's shunning his duties at the ranch, and holds himself responsible for what happened to Tim.

Hollywood starlet and gossip-rag fodder, Mindy Fanshaw, arrives at Heartland under the pretext of honing her non-existent riding skills in anticipation of an upcoming role. Almost everyone is thrilled at the prospect of having Fanshaw in their midst, but a confidentiality contract signed by all puts a damper on the excitement. Mallory is found to be hiding out in one of the dude ranch cabins, having been aided in her 'escape' from the boarding school by young Jake. Mallory shows herself to be the most star-struck of all by collecting items Mindy has used around Heartland, planning to sell them on eBay so she can repay Jake for the money he spent helping her. Mindy shows she's a manipulator par excellence when she digs into the Ty/Amy/Caleb 'triangle', and attempts to pit the three against each other. When she ropes Caleb into taking her on a trail ride, she insists on riding an ailing Pegasus, ignoring Amy's warning that the horse should not be used. This results in a calculated photo-op for Mindy with the ubiquitous paparazzi, and an injured Pegasus.

Lou's New York friend Mackenzie has asked Lou if she can have a simple wedding at heartland and Lou's in the process of getting everything arranged. Amy has started working with one of Lisa's horses, the animal is moody and is possibly cursed...

Lou continues to chat on-line with the guy that Lisa connected her up with and agrees to meet him. Meanwhile an oil company prospecting (and blasting) near Heartland has upset everyone except two dude Ranch guests who are addicted to fishing and Lou's cinnamon rolls. Caleb tries to mend fences with Amy but when Ashley moves into his trailer things get more complicated.

Amy and Caleb continue to battle over Ashley's staying at his place. Meanwhile Val may need Ashley but is unable to seal their rift. Ty is upset because his former probation officer brings a couple of troubled kids to the dude ranch. Peter continues to try and charm Lou.

Kit asks Ty to help her re-home a horse that she was given. Amy agrees to help Caleb with team roping but backs out when it means being around Kit and Ty more than she wants. Jack and Tim lock horns about their last competition in the Hudson Derby when Lou resurrects the event as a fund raiser to help Mrs. Bell and others with some county legal problems.

Spartan, that horse that Amy and her mom rescued, is stolen. When Spartan turns up at a horse auction and is bought by Wes, the man who tried to burn down the Fleming's barn, Amy is determined to get him back, despite not having the proper bill of sale. Meanwhile Lou tries to keep it quiet that she's dating the oilman, Peter.

When Spartan starts to refuse jumps, Amy takes him to a first nations horse trainer that used to work with her mom. Meanwhile Ty struggles to gentle Harley, his new horse, on his own. Peter books the entire dude ranch and while Lou is still trying to keep their relationship a secret, she learns something about Peter's past that throws her.

Ty and Amy finally get some alone time when they make a trip up to the mountains to feed some wild horses, but Ty passes out with a high fever and a blizzard makes their remote location a problem. Lou finally comes clean with Jack on the fact that she's dating an oilman. Ashley is upset to learn that her mother sponsored Caleb on the rodeo circuit to separate them.