When an irate Grant, Ty's travel buddy shows up at Heartland to punch out Ty for "kissing Blair" the disclosure puts Ty and Amy's relationship in jeopardy. Meanwhile finding out that their marriage was not legal puts Caleb and Ashley into a turmoil. All the relationship drama makes Lou question her marriage with Peter.
Tim decides to enter his racehorse, Lightning Dexter, in claiming race despite Amy's objections. Amy and Ty's troubles are aggravated when Chase comes to town and offers to put in a bid on Dexter. Meanwhile Lou finds out that she's pregnant and though Peter comes home, he really needs to be in Dubai.
Jack resists taking a trip to France with Janice while dealing with some old memories resurrected by remodeling Marion's room into a nursery. Caleb asks Ty to be his best man but has difficulty asking him to move out as Ashley wants. Amy agrees to be a bridesmaid at Ashley and Caleb's wedding.
Amy finds that she's over-committed when she promises to "de-sensitize" three horses for the local police. Deciding that she needs help she calls in Chase. Meanwhile Amy's returning the last of Ty's things throws him and when Jack discovers that Ty is skipping classes and not showing up to help Scott, Jack proposes a road trip.
When famous Olympic trainer Stewart Forrest hires Amy to coach his Olympic hopeful daughter, Amy feels that he's pushing her and her horse too hard. When Amy again gets Chase's help Ty is concerned. Meanwhile, Jack is concerned that Mallory is neglecting her horse, Copper. Lou discovers that while Peter is home with her, his business in Dubai is in crisis.
Everyone at Heartland is concerned by the bad publicity surrounding Olympic Trainer Stewart Forrest's lawsuit against Amy. Even Chase pulls his horses from Amy's training. Ty lends Amy his support and Lou does a little investigating. Meanwhile Caleb returns from his honeymoon alone. His wife, Ashley, has remained behind in Italy for an additional week with her mother.
Caleb's rodeo buddy Bryce returns from Afghanistan in a wheel chair and asks Amy to get his horse back into condition so that he can sell it. Amy would rather convince him to try riding again. Caleb's wife, Ashley has still not returned from Italy. Jack gets a call from the Foothills Cowboy Hall of Fame but it turns out it's not for what he expects.
Ty and Amy take on a pair of Clydesdales with the help of Sugarfoot. Lou's water breaks while Peter is out of town. When a horse crazed boy and his mom show up at Heartland, Tim learns that he's got a son that he never knew about.
Peter and Lou bring the baby back to Heartland and invite the in-laws for the naming ceremony. Scott drops by Ty's new place with a motorcycle requiring some work. Amy's training of Tim and Janice's new racehorse starts showing results. Tim decides to disclose the secret about Shane.
When Amy works with a chuck wagon horse she discovers an impediment that could put the entire team in danger and change the dynamics of a prominent chuck wagon family. Meanwhile, everybody at Heartland deals with sleep deprivation as Lou and Peter desperately try to get their baby to sleep at night. Mallory thinks she's found a solution, but her sleep training method ends up pitting Lou and Peter against each other. And Caleb surprises Ty when he returns home to the trailer from the West Coast... without Ashley.
Amy helps to restore the confidence of a troubled, young trick-rider so that she can get back on her horse and perform again. Meanwhile, Ty and Amy's plans to raise the spirits of a freshly separated Caleb with a night out on the town go completely awry. And Jack is so fed up with the full house at Heartland, along with the line-ups for the bathroom, that he decides to build an outhouse. Peter gets Jack's hint and comes up with an interesting housing idea for Lou.
A friend from Jack's past shows up at Heartland when one of their old band mates passes away. Lou and Lisa secretly try to gather the other remaining members for a reunion performance to celebrate Jack's birthday. Meanwhile, Amy works with a horse that won't stop bucking as Caleb becomes smitten with Kelly - the horse's sassy and attractive owner. And Mallory meets a young country singer wannabe who seems like her perfect match... except for the fact that he idolizes her dad.
When Shane arrives to stay for the summer, Tim tries to impress all three of his kids with a "really cool" Western day trip. Meanwhile, a rodeo friend of Caleb's has a unique, and somewhat crazy, request for Ty to supercharge his "ride". And Mallory is devastated when she learns that Lou may not trust her with baby Katie as much as Mallory thought she did.
When Ty visits Mrs. Bell to thank her for paying his school fees he and Amy are surprised to learn she's moved out of her home, and away from Sugarfoot. Meanwhile, Shane competes with Janice for Tim's attention and ends up finding another cowboy to look up to. Mallory starts to fall for Austin, but can't help wondering if he has an ulterior motive for getting close to her. And Soraya takes some life advice from an unlikely source... Caleb!
When Tim's young racehorse Cisco is stolen on the way to his maiden race, Amy and Ty get help tracking him down from an unlikely source -- Ty's step-father, Wade. Meanwhile, when Lou goes off to work, Peter is left to take care of baby Katie and ends up guarding a secret that could break Lou's heart. And Caleb finally convinces Kelly to go out with him, only to have a serious curve-ball thrown his way as he arrives for their date.