Late last year, our own Usama Jawad reviewed Batman - The Telltale Series at which time Episode 1: Realm of Shadows was made available for free on some platforms. Since then, all five episodes have been released but if you've yet to get further into the series then this may of interest to you.
Without much fanfare at all, it seems that Episode 2: Children of Arkham is now available as a free download on the Microsoft Store for Xbox One.
All you need to do is head on over to the product page on a computer, click on 'Get it now' and, if prompted, sign in with your Microsoft account. From there, all you then need to do is click on 'Get' which will complete the transaction and push the download to your Xbox One.
It's worth noting that attempting to purchase the title via the Xbox app on Windows 10 may or may not offer up the title for free. If you encounter this situation, you should be able to use the aforementioned instructions to get Episode 2: Children of Arkham for free.
At the time of writing, download speeds for the title have been rather slow, so if you do snap up the game for free, you will need to exercise some patience if you're particularly keen to jump into the second episode of Batman - The Telltale Series.