Hi,
You reply to the show cause notice giving valid reasons for your absconding.
Also send them a formal resignation Letter again stating the reasons for the same.
Please send both letters by registered AD mail or go personally and handover the same to HR and take acknowledgement for both the letters. You may have to offer to pay salary in Lieu of Notice, if the company so demands.
Thank you,
Regards,
R. H. Kavarana
HR Manager
Mumbai