This only makes sense in context. There is a sentence before this one. Take a look at that sentence and the meaning will be clear.
in case of = preposition 前置词, and is used exactly like any preposition.
2011年4月13日
2
0
0
"I must, in case of her impromptu bursts of tears." 'Impromptu' can be an adverb or adjective, but never a noun. It cannot become plural. :)