Chabad.org — English translation + Rashi
Torah Temimah (Pesachim 93a): those who do the second include the shogegin, anusin, and mezidin.
English: The Sages taught: these are they who offer the second: … the shogegin and the anusin and the mezidin, and one who is tamei and one who was on a distant road.
Liability mapping — the second month is both opportunity and, in some cases, a new locus of obligation.
Missing the first for reasons beyond one’s control does not always cancel the second; the Torah keeps the door open and the duty alive.