Sonnet C begins a new series after (1) an alleged period spent "on some worthless song," for which the poet chides his Muse, (2) who is now to redeem this idle time, (3) and to survey his love's sweet face to see if in the interim Time have graven any wrinkle there. If Time has done so, the Muse is to write satires against Time.
(4) Give my love fame faster than time wastes life,
So thou prevent'st his scythe, and crooked knife.
We are overtly reverting to the theme developed in Series I, which is in a way carried on in Series II and in Series III, but not in Series IV, where Shakspere defends himself for not carrying on this theme. Now in Series V he returns to that first theme.
Sonnet CI (1) asks what amends the truant Muse shall make for this neglect "of truth in beauty dyed," since truth, beauty, and the Muse depend on "my love." (2) The Muse may answer that truth needs no color, beauty no pencil. This is the defense the Muse had made in Series IV. (3) But the Muse is not to be dumb because love needs no praise, since she must make the friend outlive the gilded tomb.
(4) Then do thy office Muse, I teach thee how,
To make him seem long hence, as he shows now.
This sonnet thus continues the Ovidian theme of the poet preserving truth against Time, and the friend is still both true and beautiful as in Sonnets XIV and LIV. So this sonnet carries on both Series I and Series III.
Sonnet CII says (1) the poet's love for the friend is really stronger, though it appears weaker.
(2) Our love was new, and then but in the spring,
When I was wont to greet it with my lays,
As Philomel in summer's front doth sing,
And stops his pipe in growth of riper days.