The main problem with "the spiral road" is that's it's inevitably too long and as the movie moves at a tortoise's pace ,it may repel some well before Gena Rowlands appearance,45 min from the beginning.
One of Rock Hudson's most ambitious movies (along with Sirk's movies and "seconds" )he does not look comfortable in this almost metaphysical tale where God himself plays a prominent part ;many scenes deal with religion and the fact that man can't do without God ,even if he devotes his life to lepers or plague-stricken crowds: there's the drunken doctor who will have a bad end ;Ives' wife ,a martyr who smiles when she learns she will die a horrible death;Ives himself on the boat ,telling his colleague he feels God in the nature,which is not obvious in the city;Hudson's memories (without flashbacks,which is better) when he recalls he told God he did not like Him and he dared Him to kill him right now;Hudson's moments of doubt and fear in the final scenes in which the sorcerer can be looked upon as an equivalent of the Devil.
Some of Mulligan's flair for eerie disturbing atmosphere would emerge again in later works such as " the stalking moon" and its "enemy" as omnipresent as he is almost invisible and "the other" in which he creates terror in the midday sun.