If the president and vice president can no longer serve, who becomes president?

The speaker of the House

Explanation:

That, of course, depends for each country, based on their own constitution law.  I'll assume here you refer to the United States of America.

If the President is unable to serve, the Vice-President takes the charge of the Presidency.

If the Vice President is also unable to take the charge, then it falls down to  the speaker of the House.

the answer is solomon northrup. he was a free-born african american, abolitionist and professional violinist that was drugged, kidnapped and sold as slave in 1841 and remained in captivity until 1853 where he regained his freedom with the of the then-governor of new york, washington hunt. he wrote and published his memoirs "twelve years a slave" in 1853, and in this text, he tells the story of his escape thru one of louisiana's swamps (the great pacoudrie swamp) in which he ended up covered in green slime from crossing the surface of the dead water.