user: Question: What is the number in the series written by Steve Blackman and had a title of "Worlds Apart"?
Columns: ['No. in series', 'No. in season', 'Title', 'Directed by', 'Written by', 'Original air date', 'U.S. viewers (millions)']
Types: ['real', 'real', 'text', 'text', 'text', 'text', 'text']
Sample row: [10.0, 1.0, '"A Family Thing"', 'Mark Tinker', 'Shonda Rhimes & Marti Noxon', 'October1,2008', '8.16']
SQL:

assistant: SELECT "No. in series" FROM "Table" WHERE "Written by" = 'Steve Blackman' AND "Title" = '"Worlds Apart"';