need to completely rest and unroot device

I need a way to completely unroot and remove the recovery menu from my htc one m8.
It is on contract but I can’t return it until I remove all traces of modification from the device.
I cannot charge the device or connect the device to any computers. ( http://forum.xda-developers.com/htc-...to-pc-t3196274 )
But the device itself has not completely drained.
Any help would be appreciated.