In "The Lady of Shalott" by Lord Tennyson, who is imprisoned in Shalott? How do we know this?

"The Lady of Shalott" is a poem by Tennyson narrated in the third person. The poem opens by describing an idyllic scene with a river surrounded by flowers and trees running from Shalott to Camelot. On an island in the river there is a tower inhabited by an nameless "lady" who is is elegantly dressed and whose singing can be heard by people passing by the tower. 

In the first stanza of Part II, the...

"The Lady of Shalott" is a poem by Tennyson narrated in the third person. The poem opens by describing an idyllic scene with a river surrounded by flowers and trees running from Shalott to Camelot. On an island in the river there is a tower inhabited by an nameless "lady" who is is elegantly dressed and whose singing can be heard by people passing by the tower. 

In the first stanza of Part II, the narrator tells us that the Lady of Shalott is cursed and must constantly weave and never stop weaving to look down upon Camelot. She can watch the world as reflected in a mirror but looking directly at the outside world will cause the curse to kill her. Thus the curse keeps the Lady imprisoned in her tower in Shalott. We deduce this from information given us by the narrator.