ad. 出其不意地, 没想到, 不料, 不知不觉地

Unawares \Un`a*wares"\, adv.
Without design or preparation; suddenly; without
premeditation, unexpectedly. ``Mercies lighting unawares.''
--J. H. Newman.

Lest unawares we lose
This our high place, our sanctuary, our hill. --Milton.

{At unaware}, or {At unawares}, unexpectedly; by surprise.

He breaks at unawares upon our walks. --Dryden.

So we met
In this old sleepy town an at unaware. --R.
Browning.