Marty Markham, a rich orphan, attends summer camp at a dude ranch where he gradually learns to love outdoor life and becomes best friends with the popular Spin Evans.
Marty gives and overall introduction to the series showing clips from episodes. Spin joins Marty at the end of the introduction to invite viewers to watch the show "starting next week."
Ollie, head wrangler for the Triple R Ranch, herds the riding stock from the range into the corral where the boys arriving for summer camp can see them. Spin, a highly competent camper from last summer, jumps from the fence onto the bare back of his horse from last year, Sailor. Bill Burnett, the camp counselor, reprimands him. Freddy is a glasses-wearing tenderfoot whose parents are very protective. Speck has a penchant for pets of all sorts. Last to arrive is Martin Markham, the spoiled grandson of a rich grandmother who has raised him after his parents died. He has even brought his butler Perkins who will stay at the camp with him helping out in the kitchen.
Martin is aloof, dressed in a suit and way too proper for the other campers. He greets them with, "How do you do, gentlemen?" He is more than happy to let Mr. Burnett carry his luggage to the bunk house and wonders why he can't have a private room. He winces when Burnett calls him Marty, not Martin. When Bill asks Marty about what sports he likes, he replies no to all of them. He does have a collection of books about horses that he brought along, although he admits to having never been on a horse. The other boys feel a bit sorry when they learn he has no parents. Camp director Logan tell Burnett that Marty's dad was one of his military officer pals who was killed in action during WWII.
Marty is fascinated by the horse at Triple R Ranch. He leaves a gate open and the white stallion corners him. At dinner, not wanting to seem too bookish, he says his hobby is playing polo.
Spin plants a frog under the covers of Marty's bed. He is so angry that the Counselor sets up a boxing match between the two.
Marty shows up at the last moment to meet Spin in the make-shift boxing ring. He and Spin go at it for three rounds. Spin asks to change bunkhouses.
All the boys except Marty mount up on their Triple R horses. They have a great time chasing a woodchuck on horseback. Ollie observes that Marty is afraid of horses and devises a plan to gently get him accustomed to being around them. He brings the horse Sky Rocket to repair a loose shoe and has Marty pet him. Oliie also reveals that last year Spin was afraid of horses at the start of camp, just like Marty is this year. Eventually, Ollie coaxes Marty into brushing Sky Rocket.
Perkins begins to pack Marty's things as he announced his intention to leave. At the evening campfire, director Logan tells the boys that he wants to win the rodeo competition against the North Fork Ranch at summer's end. Freddie is homesick and wants to leave with Marty when he does. Marty spends lots of time brushing his horse Sky Rocket. The boys short sheet Marty's bunk; he just takes it in stride as a sign that the others are beginning to accept him. When Freddie is heard crying from lonesomeness in bed, Marty takes the blame for it. He firmly announces, "I'm staying".
Marty's friends help him 'fix' his brand new jeans. The boys learn about horses and riding. Marty blows away the others with his knowledge.
Marty is embarrassed by not knowing how to ride a horse so he does something drastic. Mr. Burnett offers to let Marty ride a horse away from the others.
Marty gets in front of the others and shows he can ride. Spin and Mr. Burnett set up a snipe hunt.
Spin and the other returning campers get Marty and the other greenhorns to do silly things in the quest to attract snipes. Perkins brings back a 'snipe' from the hunt.
The tenderfoot give the older boys a little payback for the "snipe hunt". Marty borrows an alarm clock from Ambitious so he secretly practice riding before the others wake up.
Burnett realizes Marty has gone riding alone. After Marty gets thrown off, Skyrocket saves him from a rattlesnake. Marty's arm is broken.
Everyone waits to learn if Marty must leave because of his broken arm. Perkins lies to Marty's grandmother so he can stay.
The boys celebrate Marty getting to stay. The boys learn calf-throwing for the rodeo.
Al and Ollie offer to teach Marty how to rope. Marty is allowed to ride again.
Marty has been teaching Skyrocket to do tricks. Perkins wants to learn how to ride a horse. Speck and Russell accidentally cross paths with a bear.
Speck and Russell are trapped in a tree by a bear. Perkins and the mule frighten it away. Marty gets his cast removed.
Marty worries about getting to go on a pack trip. Freddie's horse runs off with him. Marty saves him.
Perkins tells the story of Jags the ghost. Spin takes a dare to sleep in the haunted cabin.
Marty and Ambitious try to scare Spin and buddies by dressing up as Jags. Back at the ranch, the boys start practicing for the rodeo. Spin won't be able to come back to the Triple R if he doesn't win.
On the day before the rodeo, Spin's horse is injured. The Triple R boys get their first look at the Northfork team.
The competition goes badly for Triple R when Freddie puts his boots on the wrong feet. Marty and Al help the team come back with their calf roping skills.
Marty pretends his wrist is hurting so Spin can win the points he needs to win another summer at Triple R but Spin doesn't fall for it. Skyrocket's trick helps Marty win the bridling contest.
Triple R wins the rodeo. Spin will get to come back to Triple R for free. Logan tells Spin and Marty they can stay to help with the round-up.
