You're playing around with the idea of a story here, but you have much homework ahead of you if you want to first craft it in such a way that it will pack a dramatic punch for the reader, and then develop the narrative technique necessary to keep from undercutting yourself at every turn.

There is some basic Story–101 stuff that you aren't taking into consideration. Right now, it's difficult to say who your story is about, as well as what your story is about. To be sure, things happen: this happens, then that happens, then other stuff happens. But none of the elements form themselves into a seamless arc that carries your characters from the beginning of the story through to the end, in such a way that events influence your characters and they, in turn, influence events.

First up: whose story is this? Alex's or Melody's. One or the other, but not both. Your failure to begin at this essential starting point leaves you with a narrative that's not really about either of them. Understand, stories are not just about things happening, but things that happen to specific characters, and how they deal with the implications. I suspect that Alex is your main character, since it is his POV that defines much of the story. However, you take enough detours into Melody's POV that things get confusing. So. If it's Alex's story, tell it from Alex's perspective. Don't show the reader anything that Alex himself doesn't know. Don't let your narrator pull rabbits out of his hat. It's Alex's story, and Alex doesn't have any rabbits. He doesn't even have a hat.

Next up: what's the problem? You poke around the edges of the problem, which is that Alex is forced to disobey his father, but, really, that's not something that's coming out of your characters themselves; that's just you trying to make a conflict. In the real world, running after your sister would clearly take priority over an ambiguous instruction to not go into the mountains, and so you risk provoking the least desirable response from your reader: "Aw, shucks. They wouldn't act like that!"

Part of your problem is that their problem is purely external. There are bad guys in the mountains and Pop doesn't want to place his children at risk. So, of course, Pop does what any attentive parent would do when danger threatens his children: he says, "Good luck. I'm outta here." Huh? Once again we hear from the reading audicence, "Aw, shucks. He wouldn't do that!"

So let's come up with a problem for Alex that your readers will accept, but, more important, let's make it an internal problem. Right now, none of your characters has a soul. They are simply wind-up dolls that you move around your stage according to your whims, but we don't know anything about what's really going on inside Alex's head. What is his relationship with his father? Troubled? Difficult? Frightening? At the moment, it's none of those. Instead, Dad proves himself to be a combination of Ward Cleaver and Cliff Huxtable (Leave It To Beaver, and The Cosby Show, for those of you born at the end of the last century), forgiving, understanding and loving (listen: do you hear it? "Aw, shucks. He wouldn't act like that!")

So let's make dad a real, three-dimensional person who we'll believe fits into the environment you've created. Loving, sure. Why not? But how about stern? Strict? Unbending? Demanding? How about a father who thinks his most important task is to instill responsibility and obedience in his children? How about a character that your reader might not agree with? That your reader might not even like? Good, kind people are fine in real life—seek them out and emulate them—but in fiction, they're death. Nothing motivates like fear, and your most efficient route to a believable problem for Alex is his fear of what will happen to him if he crosses his father.

And never underestimate the value of thwarting your readers' expectations. If you present Dad as a stern, unrelenting disciplinarian at the outset, then allow him a touch of compassion and understanding at the end, you will offer something surprising to your readers, which they will thank you for.

Actually, I think you think you've already established this relationship between Alex and his father. You haven't. We don't really know anything about their relationship, since all we get is action and dialogue. As if you were writing a screenplay. You're not. You don't have a camera, you have no visual clues to accompany your characters' actions. We don't get to watch facial expressions, body language, tone of voice, the way a movie-goer might, and there's no musical score in the background. All those deeper, supporting elements have to come through words alone, and so far, you haven't given us any. Until you anchor your narrative around this relationship, Alex will not be understandable. We'll watch him doing stuff, but without access to his internal motivation, it won't mean much.

Understand: the bad guys on the mountain are your outer story. That's the part where the world beyond tramples over your main character's life and kicks him in the butt. All good stories need a situation where events in the larger world beyond intrude on your character's private lives, forcing them to do something. But what they do, and why they do it, will come from the inner story. You need both. Right now, your outer story runs along its own track, but without an inner story for Alex, it's all incomplete.

What might that story be? Who knows. It could be anything. I'd say that it needs to present Alex with an insoluble choice. If Pa has to leave, his absence itself has to constitute a problem, one that Alex is forced to solve. If, for example, someone is scheduled to come out to the ranch to discuss important business with Pa, and Pa's not going to be there, then Alex must take over. Let's say the important business is financial in nature, and concluding it successfully will mean the family gets to keep the ranch. (Hey, I'm making this up as I write. I didn't say it was good, or that you should use it. Only that you should be doing something like it.) And so now, Alex's detour into the mountains becomes a serious problem for all involved. It's not just an abstract feeling that, "Pa wouldn't like this." It's a real problem. And now, instead of your reader's throwing popcorn at the screen, they're asking a much more desirable question: "Gosh, what's he gonna do now?" Get them asking that, and they'll keep reading.

Now, for Melody: why does she leave? Well, you could just chalk it up to the simple fact that children are idiots and do stuff all the time that doesn't make sense. "Don't do that," you tell them. "Okay," comes the reply. Then they do that. (Repeat, over and over again, until they're 18 and move out of the house).

However, you've already put some pieces in place, ready to be used more efficiently than is now the case. You have bad guys in the area. Clearly an example of conditions in the outer world that are beyond your characters' control, but to which they must adapt. Instead of your contrived trip into the mountains to rescue Melody (which falls flat as a problem, since all that's required is to go after her and pull her out of the ditch), drop the mountain thread altogether and just have the bad guys show up, like Bogart in The Desperate Hours and create the problem for Alex and Melody. That would also eliminate Pa's unbelievable choice to leave his kids alone when he already knows there are bad guys in the area. That's the thing about bad guys: you can't predict them. They just show up. So... have them just show up.

Throughout, you must keep in mind that problems are your stock in trade. A story without problems is no story at all. So, an arc that follows this path:

Problem discovered > Problem solved > End

isn't going to be worth much. Right now, your problems all seem to follow this path. First Melody runs away. Then Alex saves her. Then, in a totally unrelated development, the stumble on the bad guys, and Alex gets tied up. But they're really stupid bad guys because they leave Melody untied, and, they forget to search Alex and so leave his knife in his pocket. Melody simply walks over to him, retrieves the knife and problem solved. They they run, but, Ah-HA! Alex remembers that there's a cave nearby, they hide, and they're safe. And then, just to make sure that no real problems appear that might interest your reader, Mr. Harris shows up. Turns out Mr. Harris saw them getting captured the night before, so, of course, he forgets that he has a loaded gun and instead runs back down the mountain to get the sheriff, trusting that the bad guys won't harm the kids while he was gone, or do something smart like take them some place else that he might not know about. Fortunately, the bad guys stay stupid throughout, the Sheriff arrests them and all's well that ends well. Except your readers are once again throwing the pages across the room and screaming, "Aw, shucks! That doesn't make sense!"

You can't do that to your reader and expect them to remain your reader. You can't keep pulling rabbits out of your hat and think you have a believable plot. And you can't keep throwing one problem after another at your characters, that are each, in turn, solved effortlessly. One problem leads to another, and another, and another until your reader cries out, "How are they gonna get out of this?" Believe me, they'll keep reading to find out.

Here's the way you want your story to unfold:

Problem discovered > Decision made > Action taken > unexpected consequences either make the problem worse, or open up a new problem, or both > repeat decisions, actions and unexpected consequences for as long as you can come up with a believable development.

Now, that narrative technique I talked about. First up: learn about to and too. You're getting them confused and you'll never be taken seriously with such rookie errors. Then, go back to the stories you've already read, that you've found enjoyable and entertaining, and reread them all, not as a consumer, but as a student. Deconstruct them. Figure out the problems, both inner and outer. Study how they open: do they set out the problem with exposition, do they place the characters in the midst of a situation and allow the nature of the problems to show themselves in the course of the action? If they're good stories, they won't open with a section like you've used, where the characters simply stand around and talk to each other, to make sure the reader knows what's going on.

Study the writers you know, who, it is assumed, have influenced you. Copy them. Try to write just like them. Do it the way they would do it. It works for art students, camped out for hours at a time in museums, slavishly copying each brushstroke of one masterpiece or another, as they try to unlock the techniques that produced the result. Eventually, they take the techniques they learn and evolve their own style. So too with writers. But at the outset, there's no better way to avoid clumsy writing than by copying someone who already does it right.

Take a look at your second section, where the children are in the swing. Read it over and over until you see why that section would have been a much better opening. Junk the opening. Get rid of Mom since she has nothing to do with anything, give your children real-world problems and try to raise the IQs of your bad guys. Stupid villains that are easily defeated make for lousy climax scenes. And if you're going to put your characters in peril, make it real. Give your reader a real, white-knuckle moment. Make things hopeless. And then, let them figure out how to get out of it. Don't pull rabbits out of your hat for them.