Behind closed doors

From Father Stephen's Glory to God for All Things:

"The phrase, “behind closed doors,” has become synonymous in English with things being done in secret – generally of an unsavory or nefarious sort. Institutions speak of an “open door policy,” and promise “transparency” to those from the outside. Closed doors have always had a sense of secrecy about them. Sometimes the secrecy hides the darkness of evil, other times it protects us from the wonder of the holy. 

''The stories of Christ’s resurrection are filled with closed doors.  ..."

As they say, "read it all."