In and Out
Yet the couple persists in looking, and the movie turns into a convoluted and, to my mind, largely improbable detective story, with Patrick developing into a supersleuth who steps into claustral, threatening places and takes enormous chances.
"Claustral". Lovely word!
Of course it immediately suggests "claustrophobia", the unreasoning fear of small spaces. Both these words are derived from Latin "claustrum", which originally meant merely a barrier, but in Late Latin came to mean an enclosure around which the barrier is placed through the process of synecdoche, in which the part stands for the whole or vice versa--in this case, the barrier representing the entire space within itself as well.
"Claustrum" gave rise to French "cloison", a partition, which gave its name to a kind of enamel-work called "cloisonné" because the piece to be enameled is made of tiny raised barriers which separate the various colours of the melted enamel. Both of these senses in turn gave Middle English the word "cloistre", which we now spell "cloister", which is specifically a religious retreat but more generally any secluded place.
It's worth noting, too, that "claustrum" still survives in English, as, predictably, an anatomical/medical term referring to some sort of barrier.
"Claustrum" has nothing to do with the word "cluster", although you'd think--if you strained your brain a little--that it could. "Cluster" is an Old English word which was also spelled "clyster" (because people spelled the way they pronounced); this came from a Germanic word, "kluster", and is probably related in some way to the word "clot".
But there was another English word "clyster", also spelled "klyster", which is completely unrelated to the "cluster" form of "clyster". This one came direct from Greek "klyster", which is derived from the verb "klyzein", "to wash out, to rinse out", and a clyster or klyster is in fact an enema.
"Clyster/klyster" is related, amusingly, to "cataclysm", which combines the preposition "kata-", "back" or "against", with the "-clys-" root of "klyzein" to produce a word that means literally "a massive flood: a deluge", but nowadays is used more generally to mean "a violent upheaval" or "a natural disaster on an enormous scale".