Big query case when for the other column

On the bigquery,below code shows 'Syntax error: Expected end of input but got keyword CASE at [4:3]' error Could you give me the advice?

Plan is for product, Date is the day which product sold

SELECT *
  CASE WHEN Plan='1 Class Pass', THEN DATE_ADD(DATE(Date),INTERVAL 3 MONTH)
      WHEN Plan='10 Class Pass', THEN DATE_ADD(DATE(Date),INTERVAL 3 MONTH)
      WHEN Plan='20 Class Pass', THEN DATE_ADD(DATE(Date),INTERVAL 3 MONTH)
      WHEN Plan='40 Class Pass', THEN DATE_ADD(DATE(Date), INTERVAL 3 MONTH)
      WHEN Plan='1 MONTH UNLIMITED', THEN DATE_ADD(DATE(Date), INTERVAL 1 MONTH)
      WHEN Plan='3 MONTH UNLIMITED' THEN DATE_ADD(DATE(Date), INTERVAL 3 MONTH) ELSE "null" END AS expire_date 
FROM `table_Transactions`