It is about a newly wed woman analyzing her relationship to this man she has only known for a month. The hand is symbolic of the fears present in her relationship.
As this woman has only known her husband for a month, she comes to a realization while lying in bed with him. Staring down at his hand, she perhaps sees her fears in the hand. In this hand, she...
I think there is a very subtle difference. hand and hand just refers to two hands not necessarily together.hand in hand implies that the hands are connected or together.