The Jan. 12 assassination of Iranian physicist Masoud Ali-Mohammadi remains shrouded in mystery. The Iranian regime, facing unprecedented political domestic opposition over last June's disputed presidential election, has named Israel's Mossad intelligence service as the most likely culprit, aided by the Americans and British. The Israelis' supposed objective: to sabotage Iran's controversial nuclear program. But in the Middle East, where conspiracy theories are a cultural pursuit, there's now another scenario. The Mossad is still the culprit, but its motivation is far murkier -- derailing the tortuous negotiations between Tehran and the West concerning Iran's nuclear project, and thus to clear...