Who can tell? It may be that there must always be growth - and that if one does not grow kinder and wiser and greater, then the growth must be the other way, fostering the evil things. Or it may be that the life they all led was too shut in, too folded back upon itself - without breadth or vision. Or it may be that, like a disease of crops, it is contagious, that first one and then another is sickened.
Agatha Christie, Death Comes as the End
contagious, depression, growth, life