"The Bitter Cup" appears to be Calapai's largest intaglio, done in 1961 and is extremely rare. A large skeletal figure hovers over the much smaller figure of a man who appears about to be overwhelmed by a vortex or a mighty wave - death claiming another soul??
This a biblical reference: drinking from the bitter cup means that you accept your fate, whatever it might be, death or unhappiness, something that can't be avoided. The term comes from Jesus Christ sharing cups of wine with his disciples, knowing that it was God's will that he would be killed.