Amy is bursting to ask Ty about the engagement ring, and why he hasn't proposed yet, but a couple of 'runaways' throw everything at Heartland into turmoil. Meanwhile, as Lou tries to keep it a secret that she knows about the ring, she and Peter must also cope with the money pit that the Hanley Farm renovation has become. Lou is under so much stress that when things start to go missing around Heartland, she thinks she's losing it. And Ty finds an unexpected surprise in the barn that could change the entire Fleming-Bartlett family dynamic.
When Ty needs some engine parts for his broken down truck he's forced to turn to the last person on earth he wants help from - his stepfather, Wade. Meanwhile, Lou goes after the financial portfolio of Lisa's wealthy ex-husband (Dan Hartfield) and learns something that could be devastating to Jack. Amy works with a miniature chuckwagon horse and discovers he may have a greater calling. And Georgie and Mallory need to put aside their differences to pull off a special dinner at Heartland.
A trip to help out an old friend at a fishing camp doesn't go as planned, and a series of unexpected events elevate it into a life-changing weekend for the entire family. Amy and Ty wind up going to the camp on their own, where a shared adventure involving a wounded foal brings them to a special moment. Meanwhile, Georgie realizes too late the real reason she and Jack have had to stay behind while Lou finds herself swamped with a flu-stricken Katie. And on top of everything, Jack and Lisa's issues come to a head.
Amy and Ty hold off telling the family their great news when they return from their trip to find everyone reeling from the devastating fire at Lou and Peter's home. Meanwhile, Jack gets another visit from Clint to learn whether he's been officially approved, or denied, as Georgie's legal foster parent. Traumatized by the fire, Phoenix won't go anywhere near Georgie and Amy must find a way to restore their special bond. And in the aftermath of losing their dream home Lou and Peter make a surprising decision that provides new hope for the future.
When a local horse show is cancelled Lou saves the day for Georgie and Mallory by stepping up to host it at Heartland. Amy trains Georgie to take on an entitled little brat from school named Olivia, while Mallory's not-so-secret crush on her coach, Jeremy, heightens. Meanwhile, Peter pressures Lou to fire Caleb as Ty tries to convince Caleb to apologize for 'the punch'. And Jack grooms his lawn to perfection - just in time to have it turned into a parking lot for the horse show. But just when everything is going smoothly, tragedy strikes.
Scott discovers that Spartan has a broken leg and Amy is forced to make the toughest decision of her life. As Amy searches her soul for the right path to take, Ty and Scott prepare for the possibility of major surgery on the horse. Meanwhile, Mallory throws herself into her job at Maggie's, avoiding Amy and the guilt that's eating her up inside - she blames herself for Spartan's injury. And Georgie decides to quit jumping Phoenix, fearful that he could suffer the same fate as Spartan.
Ty's future as a vet is in serious jeopardy when he's blamed for a shocking fatality at Scott's clinic. Amy is determined to help Ty get to the bottom of what really happened at the clinic in order to save his career. Meanwhile, Lou has to put an end to all of Caleb's unsolicited and unwanted help and inappropriate attention toward her domestic needs. And Georgie gets in tune with her musical side in order to score a coveted gift from Lou and Jack.
To clear his own name, Ty searches for damning evidence to prove Jeremy was behind Buckingham's death. Meanwhile, Amy attempts to find a way to get Spartan to face his extreme fear of the jumping pen - his life depends on it. Lou and Peter's romantic weekend at the Dude Ranch is interrupted by a surprise visitor... Peter's ex-wife, Eden. And against Tim's advice, Mallory turns to the internet to find romance for Jack.
Amy is having trouble dealing with a roping horse that only wants to buck and Caleb, who isn't sure he wants to ride broncs anymore. Meanwhile, when Shane shows up at Heartland for a surprise visit Tim and Miranda are forced to decide where their secret relationship is really headed. And Ty gently pushes Jack to consider accepting a cool job offer that could land him right back in the excitement of the rodeo scene.
Amy and Lou help Georgie regain her confidence as a showjumper when Olivia makes her question her place in the family. Meanwhile, one of Stumpy's cattle is found dead and the possibility of mad cow disease has Jack and Tim very concerned about their own herd. And Lou finds something that makes her wonder exactly what kind of tacky wedding Amy and Ty are planning without her input.
With the threat of losing Phoenix looming over their heads, things become even more complicated at Heartland when Georgie gets a surprise visit from her brother Jeff. When Jeff reveals the real reason for his visit the family is faced with the possibility of losing Georgie as well. With all the drama at home, Amy has second thoughts about going on a road trip to Las Vegas with Ty. Meanwhile, Peter suggests a life-changing idea to Lou that she finds impossible to wrap her head around and an increasingly stressed out and overworked Jack ends his partnership with Tim - ...