пускаться во все тяжкие

Etymology
From the professional jargon of bell ringers, where refers to a bell. Thus, the phrase originally meant “to start ringing all the bells”, later reinterpreted by association with the expression.

Verb

 * 1)  to engage in a reprehensible activity without restraint, to indulge in vices (e.g. drinking, dissoluteness, etc.), to break bad
 * 2)  to not scruple to use any means, to not be squeamish about any means one uses