Final answer:
Atticus interrupts the Missionary meeting asking for Calpurnia because he receives a call from Aunt Alexandra informing him that his children, Scout and Jem, are missing.
Step-by-step explanation:
In the book "To Kill a Mockingbird", Atticus interrupts the Missionary meeting asking for Calpurnia because he receives a call from Aunt Alexandra informing him that his children, Scout and Jem, are missing. Atticus becomes concerned about their safety and leaves the meeting to find them.