Mac os 10.13.2 upgrade appears to have broken my mac book pro
After signing in my mac book pro displays a no entry sign on a grey screen. It is now unusable. This is after I left it completing a Mac os 10.13.2 upgrade overnight. I left the iMac doing the same and all is well. What do I do to resurrect my mac book?
MacBook Pro, macOS High Sierra (10.13.2)