How to resolve a black screen after High Sierra

Yesterday I upgraded from Yosemite to High Sierra after doing a time machine backup on my MacBook Pro. The installation took a while but was successful. Once the computer restarted, the "home" screen showed icons to mine or my wife's login. i clicked on my login icon and was able to access files. I then installed Turbotax 2017 successfully. Then I logged off, expecting to see the "home" screen with the two login icons so that my wife could access here files. However, no such luck. Instead, I now get a COMPLETELY black screen...no icons, no mouse pointer nothing. I did a hard shut down and reboot with no luck...same results. Please help.