The CIA was not above using people that were close to Castro to kill him. One of his old lovers knew the type of man that Castro could be. So when the CIA approached her and asked if she would be willing to help them kill Castro, she agreed. Even though they were no longer a couple, she still had a key to the place where he stayed and she knew her way around. The plan was to go there while he was away and find something that she could put poison pills into that he would ingest, either food or water.
There was also the idea that she might be able to trick him into eating the pills outright, but that was highly unlikely. The woman, Marita Lorenz, hid the poison pills given to her by the CIA in her cold cream so that no one would suspect anything when she went to the house. She used her key and let herself in, she then opened the jar of cold cream to extract the pills. It was then that she realized her mistake.
The pills had melted in the jar of cold cream. There was no way that she would be able to get him to ingest an entire jar of cold cream so she decided to abandon the mission and just leave. It was when she was heading toward the door that Castro returned home. He asked her if she was there to kill him and she replied that she was.
Castro then offered her his gun and told her to just shoot him if she wanted to kill him. She pointed the gun at him but realized that she couldn’t kill him. Castro told her that no one could kill him. She may have come the closest of anyone to killing the Cuban leader, but she too failed.