twoway line simple problem

Dear All,
I am trying to use twoway line Suppose I have data of the following type:

id year returns
1 2000 20
1 2001 30
1 2002 50
1 2003 40
1 2004 30
1 2005 20
2 2000 10
2 2001 30
2 2002 50
2 2003 40
2 2004 20
2 2005 30


I would like to plot returns for id one and two over time. seems like:

should do it. And it does, sort of. For some reason, Stata adds a third line that connects the first and last observation of the id1 return variable.

Is there a workaround, or should I be using a completely different function?

Thanks in advance!