Checkmate Threats

Mikhail Tal faced the threat of checkmate in one against Johann Hjartarson in Reykjavik in 1987. The game as a whole shines as an example of Tal's attacking skill late in his career.

White to move

How did Tal defend?

A student with whom I am playing an unrated training game on Chess.com brought this game to my attention. We are exploring the main line of the Spanish Opening.