If you keep getting rejections it might not be your plot that’s the problem but flat and boring characters.
Remember the last good book you read? I’m guessing you enjoyed it because there was at least one character that captured and held your interest. Creating great characters is one of the keys to good fiction and with that in mind I’ve created a short guide titled Write Characters-Creating People Readers Will Love.
It’s available at Amazon, Barnes and Noble and Smashwords and just 99 cents. I hope you find it useful.