I have a question about filtering.

I want to define butterworth bandpass filter, with lower frequecy is 0.1Hz, high frequecy is 70 Hz, and the order is 4. However, the plot gives me a vertivally straight line connecting a point with gain of 1 at 50HZ, and another point with gain of 0 at 50Hz. I do not think it is a correct plot, since at the higher frequency region, I should get a curve instead of a straight line.

Please point out my mistake.