well thats your answer, your plant is freezing, thats why its going to a better life! without being smoked!!!!! dont open a window, and check the indoor temperature, if its under the 20°C its gonna die anyway... and ill give you a lit advice put a plate under the pot, or something, water only when that plate is absolutely dry for a couple days, i only water my plants every sunday...

Dont open the window at night... comeon!!!