Lambing season is in full-flow at Borough Farm. Wendy the sheep has lost track of her lamb, Sam. Jake and Mist have to work hard to reunite the pair.
The pack go off in search of The Legend of Borough Woods, a ewe who went missing from the flock some time ago, and who has been living in the woods ever since. Whoever finds her will become the boss's favourite dog. Who will succeed?
While enjoying a cliff-top view with Mist, Jake slips and falls. While trying to get back up, he encounters Sven the seal, from Sweden. Sven tries to help him get back up the cliff, by showing him the best route, and the two become firm friends. Meanwhile, anxious for her companion, Mist goes to get the boss to help rescue him.
It's now June, and the lambs are now "teenagers". The dogs need to move the flock through the woods to fresh grass on Windcutter Down. This gives plenty of opportunity for mischief from the sheep. Mist has to deal with a ewe who has got herself stuck upside down.
Mist competes in her first sheepdog trial. Unfortunately, she gets overwhelmed by the occasion and the desire to do well, and makes a big mistake trying to impress everyone. She meets up with her siblings Drift and Storm, whom she hasn't seen since they were all pups.
It's the middle of a summer heatwave, and there's been no rain for weeks, so water is scarce. Ernie has to drink his own bathwater, and the ducks' pond has dried up completely. The ducks - Joyce, Steve, Josie and Jessica - enlist Mist's help to find some new water.
When Fern overhears a whisper that she isn't pulling her weight at Borough farm, she is crest fallen. However, when Beatty the ewe gets stuck in the pond, with her fleece waterlogged, it soon becomes obvious that it is going to take a special sort of dog to save her. Right on cue Fern the swimming sheepdog wades into action.
Swift is not only the oldest sheepdog at Borough Farm, she's also the proudest. So when she's overlooked for the tough job of bringing home the rams, she sets out to prove that she's still up to such a challenge. However, the rams, led by the fearsome MacPhereson, have different ideas, and it takes the timely arrival of Swift's son Ernie to save the day.
Mist's second sheepdog trial is far trickier that the first. She doesn't just have to pen the sheep, she has to find them in the first place. When she discovers that the sheep in question are the stubborn and downright dangerous MacPhereson sisters, she understands why all of the other dogs have refused to even try. Mist uses every trick to move the cantankerous quartet of sheep through countless obstacles and finally into the pen. Everyone cheers and Mist soaks up her moment of glory.
A dark monster lurks around the valley, and panic is spreading amongst the Borough Farm ewes. Mist and Jake investigate, and with the aid of Helen the Horse and Sven the Seal, hatch a plan to save the flock. As dusk settles, a thousand sheep fill the valley, determined to prove that there is no place for a Beast at Borough Farm.
If there's one thing that ducks don't take to, it's a tree falling into their pond. So when the worst happens, Steve and his lady ducks waddle to Mist's yard in search of help. But when they arrive they find that the dogs have a problem of their own - a flood! While the lady ducks make use of the dogs' new pond, Steve wanders into the dog kennel from where he has some surprising news. "I've laid an egg, and I'm not coming out until it's hatched," leaving Mist with a problem to solve.
A heavy fall of winter snow is enough to test even the hardiest of animals. So when MacPhereson the ram wanders miserably away from the other rams, his chances don't look good. Mist sets out on a mission to find the old ram, and after a bizarre meeting with a herd of singing ponies, she finds MacPhereson, and persuades him that MacVicar, MacCrae and the others still need his company.
The winter's work has taken its toll on the Borough Farm dogs. Swift announces her retirement, Gail is feeling stiff in her joints, and Ernie is suffering with an injury. With the lambing season just around the corner it looks as if the pack are going to be short pawed. To everyone's surprise Jake introduces his three month old son, Eddie, whom he tells them will be a fine addition to the pack. Everyone is delighted apart from Mist, who wonders how life will change now that she is no longer the puppy in the pack of the Borough Farm sheepdogs.
