The quest for Forbidden Knowledge is a main theme which runs through Mary Shelley's novel Frankenstein. Not only is knowledge important to Victor, knowledge is also important to both Walton and the creature.

Victor

Victor's quest for knowledge is obsessive and oppressive in nature. Not only does he fail to care for himself during the many years it takes to reanimate life ("I had worked hard for nearly two years, for the sole purpose of infusing life into an inanimate body. For this I had deprived myself of rest and health. I had desired it with an ardour that far exceeded moderation."), his obsession forced him to ignore his family and friends. Quotes which show the danger of knowledge for Victor are as follows.

You seek for knowledge and wisdom, as I once did; and I ardently hope that the gratification of your wishes may not be a serpent to sting you, as mine has been.

Learn from me, if not by my precepts, at least by my example, how dangerous is the acquirement of knowledge, and how much happier that man is who believes his native town to be the world, than he who aspires to become greater than his nature will allow.

Seek happiness in tranquility and avoid ambition, even if it be only the apparently innocent one of distinguishing yourself in science and discoveries.

The Creature

The creature's search for knowledge revolves around his desire to know who he is, who his "father" is, and what it means to be accepted/loved. His unveiling of a few of the questions leaves him feelings more alone and lost. Therefore, the creatures search for knowledge is harmful to himself (in the same way Victor's is). While the quote does not refer to knowledge being dangerous directly, a reader can infer from the creature's feelings what the possession of the knowledge does to him.

But Paradise Lost excited different and far deeper emotions. I read it, as I had read the other volumes which had fallen into my hands, as a true history. It moved every feeling of wonder and awe that the picture of an omnipotent God warring with his creatures was capable of exciting. 

Everything is related in them which bears reference to my accursed origin; the whole detail of that series of disgusting circumstances which produced it is set in view; the minutest description of my odious and loathsome person is given, in language which painted your own horrors and rendered mine indelible. I sickened as I read.

Walton

Walton's own quest for knowledge is compared to Vcitor's through the warnings Victor gives to him. In the beginning, Walton's own obsessive nature, regarding the quest for knowledge, is noted by his unwillingness to give up his voyage to the pole. Quotes which refer to Walton's quest for knowledge being dangerous are as follows.

These are my enticements, and they are sufficient to conquer all fear of danger or death, and to induce me to commence this laborious voyage with the joy a child feels when he embarks in a little boat, with his holiday mates, on an expedition of discovery up his native river.

One man's life or death were but a small price to pay for the acquirement of the knowledge which I sought; for the dominion I should acquire and transmit over the elemental foes of our race.