Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_11981 ( "Airing date" text, "English title (Chinese title)" text, "Number of episodes" real, "HD format" text, "Highest average point ratings" real, "Genre" text, "Official website" text )

### Question ###
What was the highest average point rating for a modern suspense show with 21 episodes?

### Accurate SQL ###

SELECT SUM("Highest average point ratings") FROM table_11981 WHERE "Genre" = 'modern suspense' AND "Number of episodes" = '21'