show.html

<template>
    
    <button type="button" class="btn btn-secondary" click.trigger="show()">Show</button>
</template>

show.ts

import {autoinject} from 'aurelia-framework';
import {View} from './view';

export class Show() {

  constructor(private view: View) {
  
  }
  show() {
    //this.view.someBoolean = true;
    
    this.view.displayThis(true);
  }
}

view.html

<template>

    <div class="card card-sm" show.bind="someBoolean">
        <div class="card-block">
            <p class="mb5">Display some stuff.</p>
        </div>
    </div>
</template>

view.ts

export class View {
    
    someBoolean: boolean = false;

    constructor(){
        
    }

    displayThis(result) {
        this.someBoolean = (result) ? true : false;
        console.log(this.someBoolean);
    }
}