MCDU Went Blank

[rsmith6621a]

Hello.

I was 85% into a 14.5 hour flight WSSS/KSEA when I noticed the 350 was flying in other direction even though the AP was still engaged. I went in to the MCDU to redirect the flighplan to another fix along the route. I could not get the drop down menu that hast the direct/add or delete etc to drop down. Then I went to clear a STEP CLIMB message and then the whole FP disappeared. I cannot recover the flight plan back to the MCDU. The aircraft currently is just flying in random direction. Any suggestion? The MCDU is just dead.