Apparently, the scanner needs the hand it's scanning to be warm. Movies didn't prepare me for this!

Aliens are weird little creatures - their kitchen doesn't feature a microwave or oven at all.

Maybe their experiments involve heating things up.

Visit the botany lab - the strange machine near the door is, apparently, a microwave.

Use it to heat up the hand.

With the hand nice and warm, the jail cell can open. We finally have a train key!

Next up - the battery.