Problems with a Lightroom catalogue disappearing overnight?

Hi,  I have had my main catalogue to Lightroom disappear over night. it was there the night before now this morning it has gone,  could anyone give me any help, i am not the best on computers but when in Lightroom usually and photoshop i am ok, all my work within lightroom has disappeared, all the photos are gone within  Lightroom,  the photos/files are backed up on hard drives, but now, all work has gone, no photos at all are showing within Lightroom,    would anyone have any suggestions please?

Thank you