Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
Who was Marcus's guest in the episode when Rufus's guest was Rory McGrath?

### Inputs:
table_name: table, columns: ['Episode', 'First broadcast', 'Rufus guest', 'Marcus guest', 'Winner']

### Response:
SELECT Marcus guest FROM table WHERE Rufus guest = Rory McGrath