The sight of Moustafa’s American passport enraged the soldier. He threw it on the ground and called him a spy. He began pounding Moustafa’s face with his fists, pushed him to the ground and stomped on him with his boots. I was shoved away. Several soldiers joined in the assault and later dragged him away.

For two weeks, we frantically searched for Moustafa. When we finally found him in Abu Zaabal military prison in a desert area outside Cairo, repeated beating had turned his face into a lump of red and blue flesh.

Moustafa was detained without a charge for more than five years. And when the Egyptian prosecutors filed a charge against him, they threw him in a case with 738 other prisoners, accusing him and others of being part of the protests and trying to overthrow Mr. Sisi’s government.

A farcical show trial plodded on for the next five years. Egyptian authorities continued holding Moustafa in a prison, where the conditions are dreadful and inhumane. The cells are filthy, infested with insects, rodents and snakes. They have no ventilation, sun or light. Moustafa and other prisoners have no access to clean water, a bed, a chair or any books.

Moustafa is living with a life-threatening absence of medical care. He is diabetic and suffers from ischemic heart disease and hypothyroidism, and has had treatment for skin cancers. The prison authorities don’t even let him refrigerate the insulin for his diabetes that the family would bring to the prison.

On Sept. 8, the Egyptian court convicted Moustafa and the hundreds of others in his case. He was sentenced to 15 years in prison. In protest, against the travesty of justice, Moustafa declared a hunger strike. We begged him not to go on strike. His health was already failing.

The hunger strike would kill him. “I know I may be able to survive for only a few weeks when I go on hunger strike,” he told us. “But I have no other option. I would rather starve to death than rot slowly and silently here in this hell.”