Inkshedding quote

II.iii.151
Maria: "Sport royal, I warrant you. i know my physic wil work with him. I will plant you two, and let the fool make a third, where he shall find the letter; observe his construction of it. For this night, to bed, and dream on the event. Farewell."

Maria is speaking to Sir Andrew and Sir Toby about their plan to embarrass and shame Malvolio. She explains part of her plan to fool Malvolio into thinking the letter she leads him to find is from Olivia, and tells Sir Andrew and Sir Toby where they will hide while the plan takes place. They are to hide so that they may witness his reaction to the letter as he reads it. She is setting up her plan to eliminate Malvolio so that he will no longer control Olivias estate or try and win her heart.