Pretty solid, and you have a good logline which draws the reader in but doesn't give too much away. Liked the main character and also the supporting characters. They were all believable and most of their actions were character driven.
Flashbacks can be way overdone but here they helped to explain the story. If I could think of a better way to present the material with a different device I'd suggest it, but I can't so I'll just leave it at that.
Sure, some parts were far-fetched (mainly with some of the dialog at the end leading up to the climax between the main character and the intruders) but with a little trimming and restructuring that can be tightened.