What is the meaning of "in-pace"?

"In pace" is Latin for 'in peace', and is part of a common inscription on tombs (requiescat in pace, rest in peace). The origin, not given, appears to be the English subtitles of a movie, A Vingança de Uma Mulher (2012, Rita Azevedo Gomes) - as you may gather, Portuguese. Based on a short story from Jules Amedée Barbey d’Aurevilly’s 1874 anthology “Les Diaboliques” (1874, "six tales of female temptresses, or she-devils, in which horror and the wild Normandy countryside combine to send a shiver down the spine of the reader"). The expression refers to the practice of immurement, walling-up, or lifelong solitary confinement, sometimes given to sinful nuns. The tradition seems to have been that of complete, utter isolation from other human beings, except that food was provided. The 'peace' of this must have resembled that of the grave. It died out in the 13th century.

In the case of Jeanne, widow of B. de la Tour, a nun of Lespenasse, in 1246, who had committed acts of both Catharan and Waldensian heresy, and had prevaricated in her confession, the sentence was confinement in a separate cell in her own convent, where no one was to enter or see her, her food being pushed in through an opening left for the purpose—in fact, the living tomb known as the "in pace." ...

"The cruelty of the monastic system of imprisonment known as in pace, or vade in pacem was such that those subjected to it speedily died in all the agonies of despair."

Immurement (Wikipedia)