How do you get back to the temporal tower in Pokemon Mystery Dungeon?

OK, this could take a bit of 'splaining. Here goes. First, you go to the beach where your partner first found you (if you don't know how to get there, you go to that intersection of four roads, the guild being to the north, dungeons to the east, treasure town to the west, and the other path at the south is the one you take.). Lapras should be there. Go and talk to him, and he will ask you if you would like to go to th Hidden Land. Say yes, and battle your way through the Hidden Land. After about 20 floors, it will ask you if you want to go to Temporal Tower. Say yes, and there you go! P.S. On that beach is an alternate, cooler entrance to beach cave. You wont believe were the entrance to Beach Cave is: It's in a cave.... on... a beach. Wow. Deep.