fat is in the fire, the

It’s too late for a rescue; a crisis is imminent. This expression already appeared in John Heywood’s proverb collection of 1546 in its present form and has continued to be used with great regularity to the present  day. A  long-lived  cliché  that  is  by  no  means  obsolete, it  refers, of course, to the way a fire flares up when grease is spilled into it, an idea soon transferred to the more general sense that damage has been done.