what happens in lines 136-138 what other character is introduced here romeo and juliet

Nurse calls within.] Anon[19], good nurse! Sweet Montague, be true. Stay but a little, I will come again. [Exit.] Romeo. O blessed, blessed night! I am afeard, Being in night, all this is but a dream, Too flattering-sweet to be substantial. [Re-enter Juliet, above.] Juliet. Three words, dear Romeo, and good night indeed. If that thy bent of love be honorable, Thy purpose marriage, send me word tomorrow, By one that I’ll procure to come to thee, Where and what time thou wilt perform the rite; And all my fortunes at thy foot I’ll lay And follow thee my lord throughout the world. Nurse [within]. Madam! Juliet. I come, anon.—But if thou meanst not well, I do beseech thee— Nurse [within]. Madam! Juliet. By-and-by I come. —To cease thy suit and leave me to my grief. Tomorrow will I send.