500 Word Critique: MG fantasy

Last month, I made the offer to critique any 500 words that you cared to share. Well, someone has sent me the first 500 words of a MG fantasy. And I want to send that person a hearty thanks for being the first to step up and get the ball rolling. :)

As promised, I have kept the author anonymous, and given my reactions to the story. The blue text in parentheses are my comments.

Prologue
The rear door of the servant quarters burst open. (this is an active opening, but I think it's also a common way to start a story, so it might be beneficial to begin with something that will set your story apart) Jayin came running out with a screaming baby in his arms (this might be the element that sets your story apart). He turned to look at the castle to see if anyone was after him yet, but he was alone. He ran toward the stables as fast as he could, holding the baby close to his chest.
(a bit wordy; 'came running' can be rephrased to 'ran,' 'as fast as he could' is implied so it's not necessary. Tightening up these sentences will make a much stronger opening)
He threw open the door to the stables and went inside, looking frantically around the room. The stacked bails of hay on the far wall caught his eye, and he rushed over to them. Carefully, he laid the baby on one of the softer bails and covered her with a nearby blanket.
(there is a lot of telling here; we need to know how Jayin lays the baby down, and what's going through his head as he does it, but we don't really need to know that he's looking frantically around the room. The 'frantic' is implied in the tone and tension of the story, plus, if he's familiar with the stables, he'd already know where the hay bales were and wouldn't need to look for them. Showing us more of what is in Jayin's head will create a connection to him, and help us feel his urgency)
(also, in the first paragraph the baby is screaming, but in the second he's putting her down; is she still crying?)
He grabbed the bridle hanging from a nail on the wall, and then opened the door of the nearest stall. A tall chestnut horse looked up at him, and then looked at the bridle in Jayin’s hands. Jayin tried to force the bit into the horse’s mouth, but the horse wouldn’t have it. He tried again and the horse tossed his head back, eyeing Jayin with irritation. (some of the detail with the horse slows things down, and we lose the tension built in the previous paragraphs)
“Come on, big fella. I know I’m not your master, but he can’t come here anymore.” (interesting, and makes me wonder why he can't come anymore)
The horse moved to the far side of the stall and refused to cooperate. Jayin grabbed a handful of oats from the manger and put the bit in the center. Confused by the scent of food, the horse opened his mouth. Jayin saw his chance, and quickly placed the bit into the horse’s mouth. He fastened the straps over the horse’s head, and then led him out of the stall.
(the word 'horse' is used a lot here, and is not always necessary)
The baby was still crying as Jayin walked over her. (I think you mean 'walked over to her') :)
(I actually had to read this again before I realized the baby is a girl, because this is the only reference; perhaps make this more obvious?)
“Shhh,” he said as he picked her up, “it’s alright. Everything will be alright.” (how is he feeling here? What happened to make him take a horse that doesn't belong to him? If you can't provide the details of the incident, that's okay, but give us some insight into the character's feelings so we can connect with him)
He tied her blanket around his neck in a makeshift sling, placed her inside, and tightened the knot so she was close against his chest. He pulled down the cloak that was hanging next to the door and threw it over his shoulders. He closed the front to conceal the baby, and then leaped onto the horse’s bare back. (lots of details, and I kind of feel bogged down; do we need to know exactly how he made the sling? Or how he put on the cloak? I think telling instead of showing would be more effective here)
“Come on,” Jayin said as he kicked the horse into motion.
(the 'said' tag isn't needed here; showing us Jayin's actions is enough for us to know who is speaking: 'Jayin kicked the horse into motion.')
They galloped across the grounds toward the castle gates (he's leaving a castle! interesting...). The gates were still open with very few guards, which puzzled Jayin. He thought the gates would be closed by now, but perhaps he had caused more confusion than he thought (this is both interesting and confusing. I think we need a bit more of what's driving Jayin. It seems like something terrible has happened, and that's intriguing, but how has it affected Jayin? Why isn't he thinking about it? Withholding both his feelings and the information here is, well, it's not quite contrived, but it's on the borderline. An impatient reader may not read further). He slowed the horse to a trot, glad that the baby had quieted down. (when did she quiet down? seems like he would notice this right away and feel something - relief?)
“Good afternoon,” he said smiling at the guards.
“Afternoon, Master Jayin. Going home to your missus?”
“As a matter of fact, I am.”
“Give her my best.”
“Will do.”
(if Jayin is leaving a castle, then wouldn't the guards recognize the horse he's riding and know it's not Jayin's? If they know Jayin, they'd know whether or not he usually rode a horse, and what that horse looked like)
Jayin passed through the gates with a nod to the guards and decended the steps leading into the city. He kept the horse at a trot until he was well away from the gates, and then nudged him into a gallop. There were several people walking down the city streets, and Jayin had trouble getting through the intermittent crowds. (a bit wordy again; perhaps trim it down?)
I don’t have time for this.
“Out of the way!” he yelled, waving his hands in the air. “Get out of the way!”
People scrambled to get off the streets, and then cursed his rude behavior after he had passed.
(I'm not sure this adds much to the story. Jayin was so careful not to draw attention to himself when he left the castle, so why would he draw attention to himself now? If something terrible has happened in a castle, and if he had anything to do with it, he would know that his only chance for survival would be to remain invisible. So he seems out of character here)

Overall, I think you've done a good job. You show the characters actions in a clear and vivid way (sometimes a bit too much, but that's a good problem to have), and there is plenty of tension. The pacing could be a bit quicker, and that can be fixed by giving the reader more information up front.

I'm curious as to what could have happened for Jayin to steal a horse and hide a baby in his cloak. I think you've set up the situtation well, and what the story needs now is more insight into Jayin's character. How old is he? Probably an adult since the guards asked about his 'missus,' but we don't know if he's young, middle-aged, or old. What is his role within the castle? The guards know him and like him, but that doesn't tell us much. We also need to know the importance of this baby. Is she royalty? Knowing these details will heighten the tension, and also create a stronger connection to both the story and the characters.

Thank you again for stepping up and sending in your work!!

As for all of you reading, what did you think? Do you agree with me? Disagree? Did I miss anything? Please weigh in with your comments!

If you would like your work posted here for critique, then send me 500 words from anywhere in your story. Or, feel free to send a query for critique.
tabwriter at gmail.com