Who and Why

Who was Iran trying to assassinate?

The target of an alleged terror plot left the U.S. recently after delivering a secret letter to Obama.  

 Arab Spring tension 

Also: 

• Key dates in the plot
• Iran denies 'comedy show'
• Clinton: More isolation

Surprising way Iran's plot was foiled

The murder-for-hire tale of the plan to kill the Saudi ambassador to the U.S. reads like a Hollywood thriller. » Mexico's role 

Also: 

• U.S. aims to punish Iran
• Suspect 'no mastermind'
• Iran rejects 'vulgar' claims