On a sunny morning earlier this year, a camera crew entered a well-appointed apartment just outside the 9th-century gates of Vatican City.
Pristinely dressed in the black robes and scarlet sash of the princes of the Catholic Church, the Wisconsin-born Cardinal Raymond Burke sat in his elaborately upholstered armchair and appeared to issue a warning to Pope Francis.
A staunch conservative and Vatican bureaucrat, Burke had been demoted by the Pope a few months earlier.
Francis had been backing a more inclusive era, giving space to progressive voices on divorced Catholics as well as gays and lesbians. In front of the camera, Burke said he would resist liberal changes - and seemed to caution Francis about the limits of his authority. "One must be very attentive regarding the power of the Pope." Papal power, Burke warned, "is not absolute". He added, "The Pope does not have the power to change teaching [or] doctrine."
Burke's words belied a growing sense of alarm among strict conservatives, exposing what is fast emerging as a culture war over Francis' papacy.