I'm reading Perfect Little Children by Sophie Hannah and it's such a weird premise and I'm baffled about what could possibly actually be happening.

The main character drives by her former friend's home 12 years after she last saw her and sees her children who are somehow still 3 and 5 years old, just like they were 12 years ago. This doesn't appear to be a sci-fi book at all and I can't figure out what could be happening so I'm looking forward to getting to the end of the book and getting it all explained.