HARI SREENIVASAN:

Tonight, our series Fault Lines takes us to Estonia.

Unlike Ukraine, where we spent the last two nights, Estonia is a member of NATO, one of the alliance's smallest countries, but among its most committed members.

Today, Estonians say they need NATO more than ever because their fears about a resurgent Russia are the highest since the country gained independence when the Soviet Union collapsed 25 years ago.

With the help of the Pulitzer Center on Crisis Reporting, special correspondent Nick Schifrin begins our report in the city of Narva, literally a stone's throw from Russia.