Finding a way or time to leave proves more difficult than you anticipated.

There's a stable that the Castello family shares with the neighbors, with only four horses inside: two that belong to them, and two that belong to said neighbors. The stable is always locked, which wouldn't be a problem for you if you thought you could get in and out quietly. Those horses aren't exactly quiet, and that barn door creaks so loudly that you can hear it from your room; it doesn't help that the stable is ridiculously close to the house.

When you're scouting it out, you notice that it's in direct view of Willem's bedroom window. It would be hard to sneak in undetected and leave quietly.