Sort Table with Row Spans

HTML

<button class="sort-table">Sort Alpha</button>
<table id="sort-table">
    <thead>
        <tr>
            <th rowspan="2">Visitor</th>
            <td>Scheduled In</td>
            <td>Time In</td>
        </tr>
        <tr>
            <td>Scheduled Out</td>
            <td>Time Out</td>
        </tr>
    </thead>
    <tbody>
        <tr>
            <th rowspan="2">Santos Angelo Borodec</th>
            <td>9am</td>
            <td>&nbsp;</td>
        </tr>
        <tr>
            <td>5pm</td>
            <td>&nbsp;</td>
        </tr>
        <tr>
            <th rowspan="2">Marcelina Mitch Whitebird</th>
            <td>8am</td>
            <td>&nbsp;</td>
        </tr>
        <tr>
            <td>4pm</td>
            <td>&nbsp;</td>
        </tr>
        <tr>
            <th rowspan="2">Vince Shayne Trussell</th>
            <td>6am</td>
            <td>&nbsp;</td>
        </tr>
        <tr>
            <td>2pm</td>
            <td>&nbsp;</td>
        </tr>
        <tr>
            <th rowspan="2">Teri Porfirio Wilhoite</th>
            <td>7am</td<td>&nbsp;</td>
        </tr>
        <tr>
            <td>3pm</td>
            <td>&nbsp;</td>
        </tr>
    </tbody>
</table>

CSS

table, td, th {
    border: 1px solid lightgray;
    text-align: center;
}
tbody th {
    color: steelblue;
}

JavaScript

$('.sort-table').click(function (e) {
    var $sort = this;
    var $table = $('#sort-table');

    var $rows = $table.find('tbody > tr:even').map(function () {
        return $(this).next().andSelf().clone().wrapAll('<table />')
    });
    $rows.sort(function (a, b) {
        var keyA = $('th', a).text();
        var keyB = $('th', b).text();
        if ($($sort).hasClass('asc')) {
            return (keyA > keyB) ? 0 : 1;
        } else {
            return (keyA > keyB) ? 1 : 0;
        }
    });

    var tbody = $('tbody', $table).empty();
    $.each($rows, function (index, row) {
        $(tbody).append($(row).unwrap());
    });
    e.preventDefault();
    $($sort).toggleClass('asc');
});