RALPH: Hamlet now returns to Gertrude, telling her to sit down and stop wringing her hands. Instead, he'll "wring her heart," meaning that he hopes to squeeze some feelings of remorse out of her.

SARAH: Hamlet accuses her heart of having become insensitive, or hardened, from "damned custom" - implying that her recent behavior has perhaps made her insensitive to guilt.

RALPH: When Hamlet says "proof and bulwark against sense", he means that her heart might be too shielded, or defended against, sense - and here, sense means sensibility, or the right kind of feeling.