unbeknown/unbeknownst to sb

 Mitsuko is an attractive divorcee, highly intelligent, relentlessly cynical, forbiddingly calculating -- and yet, unbeknownst to herself, desperately vulnerable. 

Jane, however, filed and won a civil case against him: a Tokyo court ordered him to pay ¥3m (around $30,000) in November 2004. But unbeknownst to Jane or the court, soon after the suit was filed, the American navy had quietly discharged Mr Deans, who returned to America and disappeared. Later, she received compensation from Japan’s Ministry of Defence, out of a discreet fund for civilian victims of crimes by American military personnel. 

  unbeknown Show phonetics adverb (ALSO unbeknownst)

  FORMAL unbeknown/unbeknownst to sb

without a particular person knowing: 

Unbeknown to me, he'd gone and rented out the apartment in my absence.