Buzz asks Mack why she is freaking out and cleaning everything. Her parents are visiting the camp and her father likes to have everything his way. Buzz greets his grandparents when they arrive and his grandfather, Jack, offers Mack advice about chopping down vines.
In the mess hall, Cole says that Robbie is acting grumpy. Robbie is upset about his breakfast and goes to the kitchen to yell at Sarah. Instead of Sarah, he finds Jay, who tells him that Sarah quit. Mack announces that tomorrow is the Harvest Moon Festival. She introduces her father to the camp. He says he comes back every year for the festival because the memories you make at camp, warm your heart forever. Mack asks Cole to cut down the vines near her cabin but Cole is still upset about being rejected by her.
In Kip's cabin, Buzz and Grace offer him advice on Marina. Buzz thinks that Marina wants to have sex with him but Grace says that it was just a kiss. They see Marina walk over to Greg's cabin and Buzz says to forget everything he said. Marina visits Greg to tell him that she is pregnant. She asks for a ride to the drug store but he's busy teaching classes that day. She takes his car keys anyway and hopes she can find someone who can drive.
Buzz and his grandfather fish out on the lake. There are splashes around them as golf balls from Ridgefield land in the lake. Jack declares war on Ridgefield. Back at the dock he tells Mack about the driving range. He has trouble tying the boat to the dock so Buzz does it for him.
Marina asks Kip for a favour, she asks him if he can drive her to the drug store and he agrees. They get in the car and Marina hesitates to tell Kip why she needs to go to the drug store. She finally tells him that she needs to buy a pregnancy test. They set off but not before Kip drives Greg's car into a dumpster. While they are out driving, a cop pulls Kip over. It is then that Kip tells Marina that he only has a beginner's licence. Marina tells the cop that Kip has cancer to try to get him out of trouble. The police officer agrees to let them go with just a warning because they are also friends with Robbie. He offers to drive them back to the camp but Kip asks for a ride to the drug store first, for cancer medicine.
Cole asks Robbie where he thinks Sarah went but he has no idea. They find Buzz and Jack in a shed planning a prank war. At Ridgefield, the four men herd goats in to the room that Roger is delivering a speech in. On their way out they run into Sarah. She tells Robbie that she got a job there to get away from Robbie.
Kip and Marina finally arrive at the drug store but it's closed. They are trapped in town now so they decide to go to a hotel for the night. Kip uses his money from darts to pay for the room. Marina thanks Kip for being with her throughout the day and Kip says there is nothing he would rather do. Kip reassures her that everything will be okay.
Mack talks to her mother about her divorce. Her parents want her to get back together with Steve and they are both angry when they hear she has had sex with Roger.
The next morning, Camp Little Otter finds itself the victim of numerous pranks. Mack asks Cole to look after her father. The four pranksters return to Ridgefield to perform more pranks. Mack's dad rides a horse away and Robbie leaves to find Sarah. Cole runs into Roger, who says the fun is over. Roger bothers Cole with the fact that he has had sex with Mack. He tells Cole to bring his horse back in one hour or he will pound Cole.
Jack confronts Mack and Buzz but he doesn't remember who they are. Roger arrives to see where his horse is but Jack has Alzheimer's and doesn't remember anything about a horse.
Kip and Marina are finally able to get to the drug store. While they walk up to the counter armed robbers hold the store at gun point. They take Kip's money and wallet and see that Marina is buying pregnancy tests. They offer advice on contraception and tell Marina that Kip is a good guy.
Robbie complains about Sarah again to Cole. He has had enough though and slaps Robbie and tells him to forget Sarah.
Buzz walks with Grace and tells her about his grandfather. They see Roger's horse near them but Buzz burps, scaring the horse away.
Mack and Roger are also out looking for the horse. She asks him what she should do about her father's Alzheimer's. He says to love him every day and just be there for him. Roger's greatest fear is going through something like that alone. They are startled when Buzz and Grace come up behind them riding the horse. Roger thanks them for finding the horse and he hugs them both.
On their walk home, Kip and Marina get into a fight. She wants to take the pregnancy test right then behind a tree. Kip tells her he loves her and will always be there for her. He even asks her to marry him. Marina says Kip is the best person she has ever met and walks into the bushes to take the pregnancy test. She walks out of the bushes and is happy to tell Kip that she isn't pregnant.
Mack tells her dad that she thinks it's time that he see a specialist. He talks to her about the camp and says he is proud of how she runs the camp.
Everyone shows up to the Harvest Moon Festival, even Kip and Marina make it back in time. Mack stares at the full harvest moon. On the other side of the lake, Roger also looks to the moon. Cole walks up and asks if he can work for Roger at the Ridgefield that he plans to open in Alaska.
Kip and Marina kiss under the full moon and she asks him about the marriage proposal. They realize that they forgot all about Greg's car until now.
Jack tells Buzz how the harvest moon got its name and they joke about it while Mack and her mother smile at them.