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_16879 ( "No. in series" text, "No. in season" text, "Title" text, "Directed by" text, "Written by" text, "Featured character(s)" text, "Original air date" text, "U.S. viewers (million)" text )

### Question ###
What are the episode numbers where the episode features Jack & Locke?

### Accurate SQL ###

SELECT "No. in series" FROM table_16879 WHERE "Featured character(s)" = 'Jack & Locke'